It's the latest example of how Congress remains stymied on the issue of guns, even over an issue they all support: Preventing terrorists from getting firearms.
"No one wants terrorists to have legal or illegal access to firearms. Keeping guns from terrorists while protecting the due process rights of law-abiding citizens are not mutually exclusive. Unfortunately, Senator Collins and others are focusing their efforts on unconstitutional proposals that would not have prevented the Orlando terrorist attack," NRA Executive Director Chris W. Cox said in a statement to CNN Tuesday.
Collins' proposal -- which would ban gun sales to people on a narrow list of possible terrorists -- is the fifth gun measure to spring up in response to the Orlando terror attack and was released the day after four other gun measures were defeated on party-line votes in the Senate.
Almost as soon as Collins and other Senate moderates -- including Sens. Tim Kaine, D-Virginia, Lindsey Graham, R-South Carolina, and Heidi Heitkamp, D-North Dakota -- had unveiled their plan on the third floor of the Capitol Tuesday, Republican and Democratic leaders gave it a chilly reception in their weekly news conferences just one floor below them, outside the Senate.
Senate Majority Leader Mitch McConnell promised Tuesday the Senate would vote on the proposal, but did not say if he would support it.
"We're going to give her an opportunity to have a vote on that and see if that's something people want to support," he said.
And Sen. Chuck Schumer, D-New York, in line to be the top Senate Democrat next year, praised Collins for working seriously on the proposal, but instantly placed the onus back on Republicans Tuesday.
"Here's the big question: How many Republicans will be willing to join her and buck the NRA and vote to keep guns out of the hands of suspected terrorists? Will enough Republicans buck the NRA to pass it in the Senate? You need a whole lot," he said.
Collins has been hustling behind the scenes to find support for the proposal -- lining up support from a swath of Republicans and Democrats -- even as public attention focused more high-profile tactics, like Sen. Chris Murphy's 15-hour filibuster last week.
"Our goal is simple and straightforward: we want to make America safer," Collins said Tuesday while outlining the plan. "All of us are united in our desire to getting something significant done on this vital issue. Surely the terrorist attacks in San Bernardino and in Orlando that took so many lives are a call for compromise, a plea for bipartisan action."
Graham, who noted that he owns an AR-15, the gun used in the Orlando attack, said the approach should be enough to sway his colleagues.
"The likelihood of someone being on this list and buying a gun to use it in a terrorist act to me is far greater than the likelihood of an innocent person being on this list. But here's the tiebreaker, we can fix the problem with the innocent person. Once the gun is bought, you don't fix that," he said.
The NRA, however, could easily tilt the balance in the Senate. Collins said earlier Tuesday she hasn't spoken to the NRA about the proposal.
Less than 24 hours earlier, in the same halls, a series of four gun measures -- two Democratic and two Republican -- fell victim to the partisan split which has doomed gun measures in the Capitol for more than a decade. It left many lawmakers visibly angry Monday evening after another mass shooting passed without any action from Congress.
But the Collins proposal is hanging in the wings as a possible outlet for Senators to say they accomplished something after the Orlando attack, even if it is guaranteed to fail in the House.
Collins said Tuesday she had eight co-sponsors, including four Republicans and four Democrats (which includes independent Sen. Angus King who caucuses with the Democrats).
New Hampshire Republican Sen. Kelly Ayotte revealed the bipartisan group, which includes Collins, King, Heitkamp, Sen. Martin Heinreich, D-New Mexico; Sen. Jeff Flake, R-Arizona; Graham and Kaine.
Sen. John Cornyn of Texas, whose on proposal on guns failed Monday, says he has some concerns about the due process issues in the bill "in the front end" but told reporters he is willing to listen to get more information on the proposal.
He said he expected a vote Thursday on Collins' proposal.
Flake urged fellow Republicans on the floor to back the plan, which he has helped craft, saying the small bipartisan group working on the bill wants to draft something that can actually pass, "not just protect one party or another."
Collins and some of her allies met with McConnell and other GOP leaders midday Tuesday and planned to present the proposal to all Senate Republicans at their weekly lunch meeting.
California Democratic Sen. Barbara Boxer, speaking to CNN's Wolf Blitzer, said she was optimistic Collins' proposal will pass.
"I believe I can predict we can get all of the 46 Democrats. All she needs is 14 Republicans. She said she is really working on it," Boxer said.