Senator Susan Collins says she’s not giving up on her fight to keep people on terror watch lists from buying guns.

“It’s not done,” Collins told The Trace Wednesday, speaking of legislation she introduced last week to close the so-called terror gap. “We are continuing to work on it. We had a meeting this week.”

The moderate Maine Republican drafted a proposal following the Orlando, Florida, shooting that seeks to ban persons on certain terror suspect lists maintained by the FBI from purchasing a firearm. Her bill, which garnered 52 votes in a procedural test last week, is designed to bridge the gap between Democrats, who have pushed hard for new gun laws in the aftermath of the massacre, and a handful of Republicans who have said they support new efforts to keep possible terrorists from buying guns, but thought Democratic measures went too far.

The Collins plan is thought to have the most realistic shot at attracting the 60 votes needed to proceed. Even so, its prospects remain dim. Senate Majority Leader Mitch McConnell opposes the bill, as does the National Rifle Association.

In interviews with The Trace Wednesday, Collins and her band of Republican colleagues reported mixed feedback from their constituents and fellow lawmakers, but vowed to push forward in their efforts to win votes from persuadable senators.

Collins says she was encouraged by an open letter in which retired Generals David Petraeus and Stanley McChrystal and other former senior military officials expressed support for her plan. She also saw momentum for the plan after a version of it was introduced in the House of Representatives by another bipartisan group, led by Democrat Seth Moulton of Massachusetts and Republicans Carlos Curbelo of Florida, Bob Dold of Illinois, and Scott Rigell of Virginia. (Curbelo, from a Florida district near Miami, and Dold, from outside Chicago, are among House Democrats’ top targets this fall.)

Despite bipartisan support, House Speaker Paul Ryan has resisted calls to allow gun regulation bills to get a vote. And McConnell has become increasingly overt in his effort to block a vote on the Collins amendment.

“We have got to move on,” McConnell said Sunday on ABC’s “This Week,” citing other legislation that requires action.

The opposition from on high leaves the nine Republicans who joined Democrats in supporting the amendment doubly exposed: Gun rights supporters can bash them for supporting a bill that tightens gun restrictions, and gun safety groups can use the plan’s failure to call for a change in power in the Senate. Such advocates, and their Democratic allies, are already hinting that even if this narrow terror gap compromise passes, it’s not enough to erase vulnerable Republicans’ opposition to more robust gun restrictions.

Senator Pat Toomey, a Pennsylvania Republican, said feedback from his state has not reached the volume it did in 2013 when he joined West Virginia Senator Joe Manchin on a plan to expand background check requirements “but we’ve definitely heard from people on both sides.”

“Yes,” Senator Jeff Flake, an Arizona Republican who supports Collins’s plan, joked when asked if feedback was angry or supportive. “Both.”

The Republicans who supported the amendment fall into two categories: Embattled incumbents seeking political cover on the gun issue amid reelection fights, or veteran senators eager to assert themselves by enacting compromise legislation.

Collins and Flake fall into the second group, as do fellow cosponsors Lindsey Graham of South Carolina, Lamar Alexander of Tennessee, and Dan Coats of Indiana, who is retiring this year.

“I’m a results-oriented guy,” Alexander said in an interview Wednesday. “When the subject is should we keep terrorists from buying guns, I want to debate it and try to get it through.”

Toomey, Kelly Ayotte of New Hampshire, and Mark Kirk of Illinois — all facing tough races this year — fall into the first group. They get political benefit from supporting a plan that they can use to deflect attacks on their more orthodox gun votes.

McConnell, seeking to keep his majority, has a vested interest in allowing the group to advance a plan, but far less motivation to allow it pass amid NRA opposition.

McConnell can duck the gun issue by refusing to bring back up the Commerce, Justice, and Science funding bill, to which the amendment could be attached, a move that a Democratic leadership aide suggested he will take. Republicans are arguing that there is no reason to allow a vote on Collins’s plan because it lacks the votes to pass.

McConnell himself took steps to facilitate that outcome last week during procedural votes, when he paired the measure with a competing proposal from Senator Ron Johnson of Wisconsin, another endangered Republican. Johnson’s bill, which only received 31 votes, would allow the Justice Department power to delay, but not block, a terror suspect from buying gun.

The Johnson countermeasure likely drew votes away from Collins’s plan by providing another means of cover to those facing potentially competitive reelection fights but who are reluctant to back Collins’s plan — such as Marco Rubio of Florida and Rob Portman of Ohio.

“Alternatives can be attractive to people who are close calls,” Collins said Wednesday.

Rubio told The Trace that he hoped Collins would add due process provisions to her plan, but “she couldn’t get there on some of those issues based on the coalition she had put together.”

Collins said Senators Dianne Feinstein and Bernie Sanders, who missed the vote on her plan, told her they would vote for it in the future, giving her 54 supporters at this juncture.

She declined to comment on whether McConnell is maneuvering` to kill her proposal.

“I am not going to impugn motives,” she said.

[Photo: AP Photo/J. Scott Applewhite]