Sen. Susan Collins, R-Maine, speaks during a Senate Appropriations Subcommittee on Transportation, Housing and Urban Development, and Related Agencies to examine proposed budget estimates and justification for fiscal year 2022 for the Department of Housing and Urban Development on Thursday, June 10, 2021, on Capitol Hill in Washington. Credit: Matt McClain / The Washington Post via AP, Pool

U.S. Sen. Susan Collins, R-Maine, said she would vote against President Joe Biden’s pick to lead the Bureau of Alcohol, Tobacco, Firearms and Explosives on Monday, making David Chipman’s path to confirmation more difficult.

The agency responsible for enforcing federal gun laws has only had one Senate-confirmed director since the position was created in 2006 amid long-standing opposition from conservatives. Collins was one of only a handful of Republicans to favor allowing a confirmation vote for that director in 2013, though she ultimately voted against his nomination.

Former President Donald Trump’s pick for the job, Chuck Canterbury — who had previously served the president of the national Fraternal Order of Police — saw his nomination withdrawn last year due to backlash from Senate Republicans.

Chipman, a former ATF special agent, faces a slightly friendlier Senate environment with Democrats holding a narrow majority in the upper chamber. But he engendered immediate opposition from Republicans due to his recent work as a policy adviser at Giffords, a gun control advocacy group. He faced tough questioning by Republican senators in a hearing before the Senate Judiciary Committee last week, particularly over his support for a ban on assault weapons.

In a statement released by the Sportsman’s Alliance of Maine on Monday, Collins characterized Chipman’s background as “unusually divisive,” saying he had “made statements that demean law-abiding gun owners.”

“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,” Collins said.

Collins has generally held a more moderate position on guns than many in her party, including supporting legislation to improve the background check system. But Maine has also been averse to stricter gun control laws, shown most recently by the failure of a 2016 referendum to strengthen background checks.

Nominations are not subject to the 60-vote filibuster threshold, so Democrats can confirm Chipman’s nomination without the support of Collins or other Republican senators. But most of Biden’s nominees so far have gotten some bipartisan support.