The intervention was the latest warning sign that the nomination of Chipman might be in trouble – which would be a serious blow to gun control advocates and those appalled at America’s shocking rates of gun violence.

“As you all know, ATF is on the frontlines of our efforts to battle gun violence,” Garland said during a visit to the agency’s headquarters on Thursday. “We are very hopeful that the Senate will soon act.”

Chipman spent 25 years at the ATF and is currently a senior policy adviser at Giffords, an organisation that advocates for stricter gun laws and is led by the former Democratic congresswoman Gabby Giffords, who survived a mass shooting 10 years ago.

Chipman was nominated by Biden in April to become ATF director. The president said: “Vice-President Harris and I believe he’s the right person, at this moment, for this important agency.”

But last month the Senate judiciary committee was evenly split on his nomination, which obliges the Senate to hold a vote to discharge him before the process can move forward. Chuck Schumer, the Senate majority leader, has still not announced a floor vote.

In a chamber evenly divided between 50 Democrats and 50 Republicans, there is no margin for error. This week Dick Durbin, the Senate majority whip, told the Politico website that “there are a lot of issues” with the nomination, adding that the whip count “is not where we want it yet, but there’s always a chance”.

The struggle is a test case for the Biden administration’s efforts to curb gun violence even as violent crimes, particularly murders and shootings, rise in many cities around the country. Activists across the country are backing Chipman’s cause.

Shannon Watts, founder of Moms Demand Action, said via email: “The Biden-Harris Administration is the strongest gun safety White House in a generation, and they continue to show it through executive actions, strong gun safety nominations and appointments, and a laser-focus on tackling the root causes of the gun violence epidemic.

“If confirmed, David Chipman would be the most qualified director the ATF has ever seen, an agency that’s purpose is to enforce existing gun laws.”

But Republicans sense a potential political trophy in their efforts to thwart Biden’s agenda and turn the second amendment into a rallying cry ahead of next year’s midterm elections.

Senator Tom Cotton of Arkansas last weekend described Chipman as a “radical gun grabber” while addressing the Hillsborough County Republican party’s third annual machine gun rally in New Hampshire – then fired several machine guns himself.

Senator Marco Rubio of Florida added in a statement: “David Chipman is a former anti-gun lobbyist who is unfit to lead the ATF. Violent crime is soaring in cities across the country. Rather than confront the real cause of the problem, Chipman seems more interested in punishing law-abiding gun owners and sharing crackpot internet conspiracies.”

The solidified opposition is testament to how the Republican party remains in lockstep with NRA, which has been mired in scandal and declared bankruptcy earlier this year only for its filing to be dismissed by a judge.

Amy Hunter, an NRA spokesperson, said of Chipman: “This is a guy who’s been paid to lobby for what the NRA considers radical gun control for the last 10 years. The position of ATF should be someone who can bring communities together, who can look out for the interests of law abiding gun owners, law enforcement.

“It should be a unifying position. His testimony on Capitol Hill made clear his extreme views on the issue and we are very much opposed to him and are spending enormous amounts of resources and energy to oppose his confirmation.”

It is not yet clear whether Democrats Joe Manchin of West Virginia and Jon Tester of Montana – both states with high gun ownership – will back Chipman. Schumer complained to reporters that, despite claiming financial troubles, the NRA spent $250,000 on TV ads encouraging people to call Manchin and tell him to reject Chipman’s confirmation.

Hunter added: “We’re working very hard to make sure that the residents of Montana, West Virginia, Maine, Arizona – we’ve been communicating with all of our members to make sure that they’re letting their senators know in those states that they should vote no on the Chipman confirmation.”

Biden suffered a defeat early in his presidency when Neera Tanden withdrew from consideration to lead the White House Office of Management and Budget due to lack of support. Failure for Chipman, on such a defining issue, would carry more of a sting and demonstrate once more the power of the gun lobby.

Larry Jacobs, director of the Center for the Study of Politics and Governance at the University of Minnesota, said: “The NRA have taken so many body blows and yet their political voice appears to still be intact.

“I think they’re looking for basically symbolic issues to show themselves to be relevant. Anyone that the Biden administration nominates who’s going to be serious about gun control, at a time when gun violence is up in America, is going to be targeted by the NRA and its supporters in Congress.”

Jacobs added: “It’s kind of a case study on what’s wrong in America, Just following the mass shootings in America you would think that there would be a reasonable response and yet that’s not possible because you’ve got organisations whose financial health depends on using the issue to gin up membership and donations.”