WARREN, Mich. — Joseph R. Biden Jr., taking on President Trump over protecting American jobs, traveled to Michigan Wednesday and announced he would change the tax code to discourage moving jobs overseas and to reward companies for investing in domestic production.

But before sketching out his plan, he took aim at Mr. Trump over new revelations from a forthcoming book by the journalist Bob Woodward that the president knowingly minimized the risks of the coronavirus to the American public.

“He had the information,” Mr. Biden said, accusing Mr. Trump of lying to the public. “He knew how dangerous it was. And while this deadly disease ripped through our nation, he failed to do his job on purpose. It was a life-and-death betrayal of the American people.”

“It’s beyond despicable,” Mr. Biden added, detailing the crises the nation faces as a result of the pandemic that go far beyond the staggering public health costs. “It’s a dereliction of duty. It’s a disgrace.”

Mr. Biden went on to rip into the president’s record on the economy, suggesting that Mr. Trump has not kept his promises to American workers about a range of issues, lashing his record on matters from job creation to keeping work in the United States rather than overseas.

“He’s failed our economy and our country,” he said.

Mr. Biden also promised to take a series of executive actions to ensure the purchase of American goods in the federal procurement process.

As part of the new plans, Mr. Biden would create a tax penalty aimed at American companies that move jobs to other countries, known as offshoring. Mr. Biden has already proposed raising the corporate tax rate to 28 percent, from 21 percent. The penalty would apply to “profits of any production by a United States company overseas for sales back to the United States,” bumping up the tax rate to nearly 31 percent on those profits.

Mr. Biden would also create a tax credit for companies that make domestic investments, such as revitalizing closed manufacturing plants, upgrading facilities or bringing back production from overseas.

“Make it in Michigan, make it in America, invest in our communities and the workers in places like Warren,” Mr. Biden said. “That’s what this is about.”

Mr. Biden gave his speech in Warren, a city in Macomb County — a place associated with white working-class voters who traditionally voted Democratic but embraced Ronald Reagan and, later, Mr. Trump. He has intensified his efforts in recent months to unveil more populist policies aimed at boosting American workers.

“I don’t accept the defeatist view that the forces of automation and globalization mean we can’t keep good-paying union jobs here in America, and create more of them,” said Mr. Biden, speaking at UAW Region 1 headquarters, where he made direct appeals to autoworkers. “I don’t buy for one second that the vitality of American manufacturing is a thing of the past.”

Thomas Kaplan reported from Warren, and Katie Glueck from New York.

President Trump acknowledged to the journalist Bob Woodward that he had knowingly played down the coronavirus earlier this year even though he was aware it was “deadly” and vastly more serious than the seasonal flu.

“This is deadly stuff,” Mr. Trump told Mr. Woodward on Feb. 7 in one of a series of interviews he conducted with the president for his upcoming book, “Rage.” The Washington Post and CNN were given advance copies of the book and published details on Wednesday.

“You just breathe the air and that’s how it’s passed,” Trump said. “And so that’s a very tricky one. That’s a very delicate one. It’s also more deadly than even your strenuous flu.”

That was a vastly different story than Mr. Trump was telling the public.

“I wanted to always play it down,” Mr. Trump told Mr. Woodward on March 19. “I still like playing it down, because I don’t want to create a panic.”

Joseph R. Biden Jr., Mr. Trump’s Democratic opponent, excoriated the president over the report. “He knew and purposely played it down,” Mr. Biden said during a speech in Warren, Mich. “Worse, he lied to the American people.”

The national security adviser, Robert O’Brien, warned the president on Jan. 28 that the coronavirus represented the “biggest national security threat” of his presidency, according to CNN’s account of the book, but Mr. Trump later said he did not remember the warning.

At the White House press briefing on Wednesday, shortly after the book’s contents were made public in press reports, the press secretary, Kayleigh McEnany, claimed that the president, who intentionally misled the public about the virus, had not lied.

“This president does what leaders do, good leaders,” she said, saying “The President has never lied to the American public on Covid.”

In public, Mr. Trump repeatedly claimed early on that the virus would disappear. On Jan. 22, asked by a CNBC reporter whether there were “worries about a pandemic,” the president replied: “No, not at all. We have it totally under control. It’s one person coming in from China, and we have it under control. It’s going to be just fine.”

On Feb. 10 he was predicting that by April, “when it gets a little warmer, it miraculously goes away.” And on Feb. 26, at a White House news conference, commenting on the country’s first reported cases, he said: “We’re going to be pretty soon at only five people. And we could be at just one or two people over the next short period of time. So we’ve had very good luck.”

But by mid-March he was claiming publicly that “I felt it was a pandemic long before it was called a pandemic.” By then, experts said, the nation had already fallen behind on the steps it needed to take to combat the virus, from ramping up testing capability to distributing protective gear to health care workers.

Elsewhere in the book, according to CNN, the former defense secretary, Gen. James Mattis, is quoted calling Mr. Trump “dangerous” and “unfit.” He said he discussed with the former director of the office of national intelligence, Dan Coats, whether there should be “collective action” to speak out publicly against Mr. Trump. And Mr. Woodward includes an anecdote about Mr. Trump being heard in a meeting saying, “My fucking generals are a bunch of pussies” who care more about alliances than trade deals.

With just eight weeks to go until Election Day, and early voting starting well before then, voters continue to disapprove of President Trump’s coronavirus response and believe that Joseph R. Biden Jr. would do a better job handling the pandemic, according to a new poll from Monmouth University.

Only 37 percent of registered voters say Mr. Trump has done a good job handling the virus, and 56 percent say he has done a bad job. More broadly, only 27 percent say the country is heading in the right direction.

Forty-four percent say they are confident or somewhat confident that Mr. Trump can put the country “on the road to recovery” from the pandemic, and 56 percent say they are not confident. The numbers are reversed for Mr. Biden, the Democratic nominee: 53 percent of voters say they are confident in his ability to put the country on the road to recovery, and 45 percent say they are not confident.

A wide partisan gap persists on the question of whether officials are lifting restrictions too quickly or not quickly enough, but over all, 58 percent of registered voters said states were moving too fast.

“Labor Day generally serves as a marker for returning to a more normal flow of life,” Patrick Murray, director of the Monmouth University Polling Institute, said in a news release. “That’s not happening this year and could be leading to an increase in anxiety levels.”

The poll, conducted from Sept. 3 to Sept 8, surveyed 867 voters and has a margin of error of plus or minus 3.3 percentage points.

Dr. Francis Collins, the director of the National Institutes of Health, took issue on Wednesday with President Trump’s suggestion that a coronavirus vaccine would be available by Election Day, as he repeatedly sought to reassure senators and the public that a vaccine would not be made available to the public unless it was safe and effective.

“Certainly to try to predict whether it happens on a particular week before or after a particular date in early November is well beyond anything that any scientist right now could tell you and be confident they know what they are saying,” Dr. Collins told the Senate Committee on Health, Education Labor and Pensions at a hearing on the effort to find a vaccine.

Dr. Collins is the latest leading medical expert to throw cold water on Mr. Trump’s prediction. Last Thursday, the chief adviser for the White House vaccine program, Moncef Slaoui, said it was “extremely unlikely but not impossible” that a vaccine could be available by the end of October. And on Tuesday, Dr. Anthony S. Fauci said the same thing, saying that it was more likely that a vaccine could be ready by the end of the year.

Wednesday’s hearing came amid growing concern over whether Americans would be reluctant to take a coronavirus vaccine, and whether the president would apply political pressure on his administration to quickly approve one to give him a boost in his re-election bid against former Vice President Joseph R. Biden Jr.

On Tuesday, a group of drug companies competing with one another to develop vaccines pledged that they would not release any vaccines that did not follow rigorous efficacy and safety standards, and a leading vaccine developer, AstraZeneca, suspended its large-scale clinical trial of a vaccine candidate after a patient experienced a severe adverse reaction.

Democrats on the panel grilled both Dr. Collins and Jerome Adams, the surgeon general, on the effect of Mr. Trump’s overly rosy statements about the prospect of the vaccine, and whether they would erode trust in the development process. Dr. Collins demurred, however, as Senator Elizabeth Warren, Democrat of Massachussetts, asked him point blank whether Mr. Trump’s misinformation would discourage people from taking the vaccine and hurt the effort to distribute it.

“I’m not sure I know the answer to that question,” Dr. Collins said, adding, “I just hope Americans will choose to take the information they need from scientists and not from politicians.”

Two national political conventions and days of protests and unrest following a police shooting in Kenosha, Wis., have done little to change the contours of the presidential campaign in that state, according to a Marquette Law School poll released Wednesday.

The new poll, of 688 likely Wisconsin voters, found Joseph R. Biden Jr. ahead of President Trump, 47 percent to 43 percent. That represented only a slight tightening from earlier Marquette polls: One in early August showed Mr. Biden leading Mr. Trump, 49 percent to 44 percent. The new survey had a margin of error of plus or minus 4.3 percentage points.

“Despite all those real-world events, there is very little change in this poll,” Charles Franklin, Marquette’s poll director, said in a video accompanying the release.

The poll was made public as Wisconsin, a swing state that helped elect Mr. Trump in 2016, became the center of the campaign in recent days. Both Mr. Trump and Mr. Biden traveled to Kenosha after the police shooting of Jacob Blake, a Black man, led to days of protests, and a 17-year-old white man was arrested on charges of killing two protesters. The new poll was conducted from Aug. 30 to Sept. 3, so it did not fully reflect the impact of their visits.

A majority — 54 percent — of respondents said that they disapproved of Mr. Trump’s handling of protests, while only 36 percent said they approved, the poll found. And 56 percent said that they disapproved of Mr. Trump’s handling of the coronavirus. But Mr. Trump is still viewed favorably on the economy: Fifty-two percent said that they approved of his handling of it.

A new poll of another key battleground state, Pennsylvania, showed that Mr. Biden’s lead there had widened. The NBC News/Marist poll found Mr. Biden leading Mr. Trump among likely voters by 53 percent to 44 percent.

Mr. Biden’s lead there was due in part to strong support from suburban voters — which were key to Mr. Trump’s victory in 2016 — and voters with college degrees, according to the poll of 771 likely Pennsylvania voters, which was conducted from Aug. 31 to Sept. 7. Mr. Biden leads Mr. Trump among suburban voters by nearly 20 percentage points.

Among independents, Mr. Biden leads Mr. Trump 57 percent to 35 percent. The two are tied with white voters, but Mr. Biden has a commanding lead among nonwhite voters, 75 percent to 19 percent. Mr. Biden also leads among women, 59 percent to 38 percent.

The poll has a margin of error of 4.4 percentage points.

President Trump’s re-election campaign and the Republican National Committee and their shared committees reported raising over $210 million in the month of August, a large amount that was nonetheless dwarfed by what Joseph R. Biden Jr. raised in the same time frame.

And officials declined to say how much cash they have in the bank, which is a key marker of what they can spend on going forward.

Mr. Biden and affiliated Democratic committees reported raising $364.5 million in August. They also have not yet said how much they have in cash on hand.

The momentum for Mr. Biden’s campaign in fund-raising and the polls came as a once-seemingly insurmountable cash advantage for Mr. Trump’s campaign has evaporated.

Ad Watch

Usually, presidential campaign TV advertising aims to influence voters in battleground states. But in the Trump era, more ads are targeting a far narrower audience: Washington’s chattering class and President Trump, America’s cable news watcher-in-chief.

On Wednesday morning, the Democratic National Committee and the presidential campaign of Joseph R. Biden Jr. bought TV airtime in Washington to debut an ad touting report last week in The Atlantic that Mr. Trump privately referred to American soldiers killed in combat as “losers” and “suckers.”

The Message

Since The Atlantic’s story broke last Thursday, the Biden campaign has done whatever it can to give it oxygen. Mr. Biden addressed it in a speech on Friday and brought it up again during a Labor Day event. His campaign has sent fund-raising emails soliciting donations off the president’s comments and circulated other news outlets’ reporting confirming the gist of the original report.

Now, six days after it first popped, the Biden campaign is trying to keep the story in Washington’s bloodstream.

The 60-second ad opens with black-and-white footage of soldiers and a reminder that 1,800 Marines died at the battle of Belleau Wood in World War I.

“But when Donald Trump was asked to pay his respects, he said, ‘Why should I go to that cemetery? It’s filled with losers,’” the ad intones, with an on-screen graphic citing The Atlantic’s reporting.

The ad goes on to cite Mr. Trump’s remarks calling Senator John McCain “a loser” and his wondering aloud “what was in it for” those buried at Arlington National Cemetery, before stating, “Donald Trump inherited everything, sacrificed nothing, scoffs at the valor of those who gave it all for America.”

Fact Check

Mr. Trump did in fact call Mr. McCain a “loser” and said of Mr. McCain during a July 2015 campaign stop in Iowa: “He’s not a war hero. He’s a war hero because he was captured. I like people who weren’t captured.”

Mr. Trump and his top White House aides have denied The Atlantic report, but the thrust of it has been confirmed by several competing news organizations, including Fox News, and no current senior military officer has refuted it.

Where It’s Running

So far, just once: in Washington during the 6 a.m. hour of “Morning Joe” on MSNBC, an hour at which Mr. Trump is known to be channel surfing. A Democratic National Committee official said the ad would also air in Arizona, Florida, Maine, North Carolina and Virginia.

The Takeaway

Every day that the presidential campaign is about Mr. Trump and not Mr. Biden is a good one for the Biden campaign. Mr. Trump’s remarks about America’s veterans have been Topic A in Washington for nearly a week now, and the Biden campaign is happy to keep the conversation going.

Dr. Anthony S. Fauci, the nation’s leading infectious diseases expert, expressed concern Wednesday morning about the example President Trump had set the night before when he held a large campaign rally in North Carolina without wearing a mask.

Appearing on “CBS This Morning” to talk about the hunt for a coronavirus vaccine, Dr. Fauci was asked whether the sight of such rallies was frustrating for him.

“Well, yes it is, and I’ve said that often,” he said. “We want to set an example.”

Some North Carolina Republicans had apparently hoped that the president would wear a mask as well.

Before the rally, Dave Plyler, the Republican chairman of the Forsyth County Board of Commissioners, was quoted by The Winston-Salem Journal as saying that he believed Mr. Trump should wear a mask.

“It’s been ordered by the governor,” Mr. Plyler said, noting the state’s virus orders. “When in Rome, do as the Romans do. When in North Carolina, do as the governor says.”

But Mr. Trump, who has worn masks in public only a handful of times, and who mocked his Democratic opponent, Joseph R. Biden Jr., for wearing one just last week, appeared at the rally without a mask. Scott Sexton, a columnist at The Journal, wrote after the rally that “red hats outnumbered masks and face coverings by at least a 100-to-1 ratio.”

Dr. Fauci said that public health measures such as wearing masks, keeping physical distance, avoiding crowds and moving activities outdoors rather than indoors “are the kind of things that turn around surges and also prevent us from getting surges.”

“So I certainly would like to see a universal wearing of masks,” he said.

A federal judge ruled on Tuesday that Texas’s procedure for reviewing — and in some cases rejecting — mail-in ballots was unconstitutional and ordered the state to change its process before Election Day.

The state’s process for verifying signatures on mail-in ballots “plainly violates certain voters’ constitutional rights,” the judge, Orlando L. Garcia of the United States District Court for the Western District of Texas, wrote in his ruling, describing it as “inherently fraught with error with no recourse for voters.”

“In light of the fundamental importance of the right to vote, Texas’s existing process for rejecting mail-in ballots due to alleged signature mismatching fails to guarantee basic fairness,” Judge Garcia wrote.

In a lawsuit filed last year, two voters said that their mail-in ballots were arbitrarily rejected because Texas officials did not believe the signatures on the voters’ ballot envelopes matched those on their applications. The lawsuit claimed that the state’s procedures, including failure to give “meaningful pre-rejection notice” to voters, violated the Fourteenth Amendment.

In his ruling, Judge Garcia ordered the Texas secretary of state to notify local election officials within 10 days that it was unconstitutional to reject a voter’s mail-in ballot because of a perceived signature mismatch if the voter is not first informed of the mismatch and given an opportunity to address the issue.

The judge also ordered the secretary to advise local election officials of new requirements for rejecting mail-in ballots because of perceived signature mismatches, including for informing voters.

Texas currently allows voters to request a mail-in ballot if they are 65 or older, disabled, planning to be out of their county during the election, or in jail but otherwise eligible to vote. The Supreme Court ruled in June that it would not require Texas to let all eligible voters vote by mail.

Benjamin L. Ginsberg is one of the top election lawyers in the nation, the go-to attorney for Republicans in nearly every major election law battle over the past 38 years — most famously, the Florida recount in 2000 in the disputed presidential race between George W. Bush and Al Gore. Mr. Ginsberg won that one. His reputation as an expert in this (often deliberately) complicated field of law crosses party lines.

Which makes an op-ed that Mr. Ginsberg wrote in The Washington Post striking. Mr. Ginsberg — who perhaps not coincidentally has the freedom that comes from having just retired from his law firm — flatly disputed President Trump’s assertions that mail-in voting is “very dangerous” and that “there is tremendous fraud involved and tremendous illegality.”

“The lack of evidence renders these claims unsustainable,” Mr. Ginsberg wrote. “The truth is that after decades of looking for illegal voting, there’s no proof of widespread fraud. At most, there are isolated incidents — by both Democrats and Republicans. Elections are not rigged.”

These are “painful conclusions for me to reach,” Mr. Ginsberg said, noting his own work in a catalog of redistricting and voter recount cases on behalf of his party, and that he served as the counsel to the Republican National Committee and to four of the past six Republican presidential nominees.

“The president’s rhetoric has put my party in the position of a firefighter who deliberately sets fires to look like a hero putting them out,” he wrote. “Republicans need to take a hard look before advocating laws that actually do limit the franchise of otherwise qualified voters. Calling elections fraudulent’ and results ‘rigged’ with almost nonexistent evidence is antithetical to being the ‘rule of law’ party.”

How significant is this? Well, imagine if Jerry Brown, the former Democratic governor of California and longtime environmental warrior, wrote an op-ed for The Sacramento Bee arguing that global warming doesn’t exist.

In a highly unusual legal maneuver, the Justice Department moved on Tuesday to replace President Trump’s private lawyers and defend him against a defamation lawsuit brought in state court by the author E. Jean Carroll, who has accused him of raping her in a Manhattan department store in the 1990s.

Lawyers for the Justice Department said in court papers that Mr. Trump was acting in his official capacity as president when he denied ever knowing Ms. Carroll.

Citing a law called the Federal Tort Claims Act, the lawyers asserted the right to take the case from Mr. Trump’s private lawyers and move the matter from state court to federal court. The tort claims act gives employees of the federal government immunity from lawsuits, though legal experts say that it has rarely, if ever, been used to protect a president, especially for actions taken before he entered office..

“The question is,” said Steve Vladeck, a University of Texas law professor, “is it really within the scope of the law for government lawyers to defend someone accused of lying about a rape when he wasn’t even president yet?”

Ms. Carroll’s lawyer said in a statement issued Tuesday evening that the move by the Justice Department to intervene in the case was a “shocking” attempt to bring the power of the United States government to bear on a private legal matter.

“Trump’s effort to wield the power of the U.S. government to evade responsibility for his private misconduct is without precedent,” the lawyer, Roberta A. Kaplan, said in the statement, “and shows even more starkly how far he is willing to go to prevent the truth from coming out.”

The Justice Department’s motion came only a month after a state judge in New York issued a ruling that potentially opened the door to Mr. Trump being deposed in the case before the election.

Ms. Carroll, a writer, sued Mr. Trump last November, claiming that he lied by publicly denying he had ever met her. In a memoir published last summer, she maintained that Mr. Trump sexually assaulted her nearly 30 years ago in a dressing room at Bergdorf Goodman.

A powerful but little-known group of Republican donors installed by President Trump to oversee the United States Postal Service has helped raise more than $3 million to support him and hundreds of millions more for his party over the past decade, prompting concerns about partisan bias at the agency before the November election.

The largest amount of fund-raising has been by Robert M. Duncan, who continues to sit on the boards of two super PACs pushing for Republicans to win in 2020, one of which has spent more than $1 million supporting the president’s re-election.

But he is only one of five Republican members Mr. Trump has named to the board — most of whom have given generously to the party — who have taken a hands-on role in trying to defend the embattled agency against accusations that it is trying to help the president win a second term by sabotaging voting by mail.

At least one of the governors expressed concerns in an interview like those voiced by the president about possible voter fraud, citing an anonymously sourced news report circulated by the Trump campaign and the president’s son Eric Trump about how mail-in ballots can be manipulated.

“If any doubt is ever raised — like in the New York Post article, or by any other reputable publication — we want to get to the bottom of that,” said John M. Barger, one of the Republican board members named by Mr. Trump and a participant in a newly formed election mail task force.

Other governors have done little to hide their loyalty to the president, even as the board meets behind closed doors to plot a strategy for handling what is expected to be a record crush of mail-in ballots this fall.