Sen. Susan Collins announced Monday that she will oppose the confirmation of David Chipman, President Biden's nominee to run the Bureau of Alcohol, Tobacco and Firearms (ATF), a blow to Chipman's prospects for a potential bipartisan confirmation vote. 

"After meeting with Mr. Chipman, listening to Mainers, and reviewing his record, I have decided to vote against Mr. Chipman’s nomination to serve as the ATF Director," Collins, R-Maine, said in a statement. "In recent years, Mr. Chipman has been an outspoken critic of the firearms industry and has made statements that demean law-abiding gun owners."

Collins added: "Although he has the right to express his views, I believe this history makes him an unusually divisive pick for this important position.  In particular, I am concerned that his confirmation would do significant damage to the collaborative working relationship that must exist between ATF, the firearms industry, sportsmen and women, and other law-abiding gun owners exercising their Second Amendment rights."

Chipman was grilled late last month by Republican senators at his hearing before the Senate Judiciary Committee. Sen. Mike Lee, R-Utah, pressed Chipman over his "aggressive" and "reckless" opposition to a bill the Utah Republican introduced that would eliminate regulations to purchase gun silencers.

In this Sept. 25, 2019, file photo former Giffords Law Center Senior Policy Advisor David Chipman speaks at a House Judiciary Committee hearing on assault weapons on Capitol Hill in Washington. Chipman is now President Biden's nominee to be the director of the Bureay of Alcohol, Tobacco and Firearms. (AP Photo/Andrew Harnik, File)

In this Sept. 25, 2019, file photo former Giffords Law Center Senior Policy Advisor David Chipman speaks at a House Judiciary Committee hearing on assault weapons on Capitol Hill in Washington. Chipman is now President Biden's nominee to be the director of the Bureay of Alcohol, Tobacco and Firearms. (AP Photo/Andrew Harnik, File) (AP)

REPUBLICANS GRILL BIDEN ATF NOMINEE ON PAST REMARKS ON GUNS

"You said, ‘The only people who benefit from this bill are gun lobbyists and criminals who want easier access to deadly weapons,’" Lee told Chipman. "How does this reflect the careful, measured judgment of one who would be in charge of enforcing our nation’s gun laws?" 

Chipman, who was an ATF special agent for 25 years, also supports banning AR-15 rifles and has a history of working on behalf of gun control groups like Giffords and Everytown. 

"We are thrilled about the nomination of David Chipman to head the ATF," Everytown tweeted when Chipman was nominated. "David will be an invaluable point person as this administration looks to fight illegal gun trafficking and end the special treatment of the gun industry."

WHO IS BIDEN'S ATF NOMINEE, DAVID CHIPMAN? 

Collins has been one of the Senate Republicans most willing to vote for Biden's executive nominees, so her opposition to Chipman signals that Chipman's nomination could be headed toward a party-line vote once it gets out of the Senate Judiciary Committee. 

Sen. Susan Collins, R-Maine, speaks during a US Senate Senate Health, Education, Labor, and Pensions Committee hearing to examine COVID-19, focusing on an update on the federal response in Washington, D.C., on September 23, 2020. Collins, a moderate with a history of supporting President Biden's executive nominees, announced her opposition to Biden's choice to run the ATF, David Chipman. (Photo by Alex Edelman / POOL / AFP)

Sen. Susan Collins, R-Maine, speaks during a US Senate Senate Health, Education, Labor, and Pensions Committee hearing to examine COVID-19, focusing on an update on the federal response in Washington, D.C., on September 23, 2020. Collins, a moderate with a history of supporting President Biden's executive nominees, announced her opposition to Biden's choice to run the ATF, David Chipman. (Photo by Alex Edelman / POOL / AFP)

Democrats, who hold 50 Senate seats and the vice presidency, however, can confirm executive nominees without Republicans' help as long as they stick together. This means focus is likely to shift to moderates like Sen. Joe Machin, D-W.Va., who represents a deep-red state and has been willing to buck his party in recent month – his opposition to Neera Tanden as the director of the Office of Management and Budget killed her nomination. 

The White House, meanwhile, is likely to press Senate Democrats to back Chipman's nomination as he moves closer to confirmation. 

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"David knows the AFT well. He served there for 25 years," Biden said in remarks earlier this year on Chipman. "And Vice President Harris and I believe he’s the right person, at this moment, for this important agency."

Fox News' Morgan Phillips contributed to this report.