The Senate is set to vote Monday on four different proposals to tighten federal gun laws, a series of votes that Democrats say are the result of nearly 15-hour filibuster led by Connecticut Senator Chris Murphy that stretched into the early morning of June 16.

But Senators’ recent comments — and past votes — indicate that there is little chance any of the measures will pass.

The Senate will vote on two proposals offered by Democrats and two offered by Republicans: California Democrat Dianne Feinstein’s proposal to close the “terror gap,” Texas Republican John Cornyn’s version addressing the same issue, a measure sponsored by Murphy that seeks to mandate universal background checks, and another offered by Iowa Republican Chuck Grassley that aims to make it more difficult for the mentally ill to purchase guns. All of the measures being considered are amendments to a Justice Department spending bill.

For any of the four proposals to pass, it will need to receive the 60-vote supermajority required to force legislation through the Senate. By offering Democratic proposals alongside Republican ones, Senate leaders have facilitated party-line voting, which, given the current balance of power in the chamber, suggests that none of the amendments will clear.

Centrist Republican Senator Susan Collins of Maine spent the weekend refining a potential compromise terror gap fix that has attracted interest from a small but potentially influential constellation of her colleagues, including both vulnerable Northeastern Republicans, staunch gun-rights supporters, and at least one Democrat. “This is something that could pass,” a Republican source told Politico. But the party’s Senate leadership signaled the bill may receive a cool reception when unveiled later today. In remarks to the Wall Street Journal, a Cornyn aide said that the Collins plan doesn’t go far enough in deferring to Second Amendment concerns, and Cornyn himself has sounded eager to move on to other business.

“The question is how long do we want to keep talking about gun control and when are we going to pivot to the national security debate,” Cornyn said last week.

Votes on the four bills currently allowed to move forward are expected to begin around 5:30 pm.

Had just a single proposal on each issue been allowed to the floor when today’s amendments were scheduled — just Feinstein’s measure, but not Cornyn’s, or just Grassley’s bill, but not Schumer’s — Senators would have faced stark, take-it-or-leave it choice, and heightened prospects of being held accountable for them. Instead, the slate of bills will allow everyone to make the claim that they voted to reduce gun violence, while their opponents were clinging to doomed proposals.

Democrats do not claim they can prevail in this round. With just 46 votes in the Senate, the party has no real shot at winning over the 14 Republicans needed to reach 60 votes for either of their bills.

But they believe they’ll achieve other goals. Democrats attracted much press and social media attention with the filibuster, and signaled that they are listening to gun violence prevention advocates and newly engaged voters demanding action after the Orlando, Florida, shooting last Sunday. The universal background check bill, co-sponsored by Senators Chuck Schumer and Cory Booker, will in particular also achieve the goal of forcing vulnerable Senate Republicans up for re-election this year to cast votes against proposals that, according to many polls, are supported by overwhelming majorities of Americans.

Americans for Responsible Solutions, an organization advocating stronger gun laws, is already running ads attacking Senator Kelly Ayotte, a New Hampshire Republican, for voting against stronger gun laws. Other Republicans targets include Ohio Senator Rob Portman, Wisconsin’s Ron Johnson, and Senator Marco Rubio, who may change his mind and seek re-election in Florida — and is already taking heat from the Democratic Senatorial Campaign Committee for his opposition to tougher gun regulations.

Mark Kirk of Illinois is another Republican on the endangered list. In 2013, he was one of four Republicans to break with party colleagues and vote for the bipartisan Manchin-Toomey bill, which extended background checks to internet sales and gun shows but not private sales, as the Democratic bill up for a decision on Monday would do. Kirk is expected to vote with Democrats again this time around. If that helps him hold his seat in November, his apostasy on gun control may be forgiven by Republican bosses, who would preserve a reliably hawkish vote on foreign policy in the bargain.

Among the other Republican votes for Manchin-Toomey was Senator John McCain, who is also expected to face the toughest re-election challenge of his career in Arizona, where his likely challenger is Ann Kirkpatrick, who currently represents Arizona’s 1st District in the House. How McCain navigates Monday’s vote on universal background checks will bear watching: If he votes against the Democratic proposal, his opponent can accuse the self-proclaimed maverick of flip-flopping in order to toe the party line. But he may also try to spin the legislation pushed by Murphy and company as failing to provide the accommodations that Manchin-Toomey included for private buyers and sellers.

Versions of McCain’s calculus apply to the Republican caucus as a whole, which heads into tonight’s votes wanting to dispose of the issue with minimal damage. Though the party controls the chamber and would need to lure just a handful of Democrats to help its bills clear the bar, the two amendments its members are proposing are not the kind designed to attract such crossover votes. Instead, the legislation’s most likely effect will be to give Republicans something to say they voted for when they are attacked for opposing what their critics call common-sense gun laws.

Cornyn’s proposal for addressing the terror gap would flag gun purchases by those who have been investigated for terrorist ties over the preceding five years, and give the Department of Justice three business days to prove to a judge that a buyer in question will commit terrorism or has previously conspired to do so. Only if that steep threshold is met would a gun purchase be denied. His plan is endorsed by the National Rifle Association. Democrats say it puts too high a burden on the federal government to be effective.

Feinstein’s amendment would also pause firearms purchases by those investigated for terror within five years. But rather than forcing the Department of Justice to prove that the individual should not be able to buy a gun, Feinstein’s bill gives the Attorney General the discretion to deny the gun purchase. (Anyone banned from gun buying under this policy would be able to appeal the decision.)

The other Republican bill up for a vote today comes from Chuck Grassley, the chairman of the Senate Judiciary Committee, and resembles a measure he and other senators offered in 2013 to counter Manchin-Toomey. The proposal does not expand background checks, and instead takes a scattershot approach at preventing gun violence by increasing money for federal prosecution of gun crimes and implementing provisions aimed at preventing the mentally ill from buying guns.

Notably, the Republican leadership is not putting forward either of two bills championed by Pennsylvania Senator Pat Toomey, another endangered Republican, who co-sponsored a background check compromise with West Virginia Democrat Joe Manchin in 2013. Seeking to play problem-solver on the terror gap, Toomey quickly put together his own proposed fix as Murphy’s filibuster was getting underway on Wednesday. His bill would require the Attorney General to create a new list of terror suspects barred from buying guns, which would be reviewed by a federal court before the names were added to the background check system’s databases of persons prohibited from gun ownership. That step seemed intended to address the due process concerns raised by gun rights advocates and their Republican allies, while preserving the teeth in the Feinstein bill.

But following debate among Republicans, Cornyn’s bill, not Toomey’s, was selected to go up for a vote opposite Feinstein’s.

The alternative terror gap compromise being assembled by Susan Collins did not emerge until after today’s Senate calendar was set. She has said she shares Democrats’ concerns that the bill from Cornyn sets too high a burden of proof in targeting persons likely to commit terrorism. Instead, Collins proposes to protect lawful gun owners incorrectly barred from gun purchases because of terror suspicions by allowing them to collect attorneys fees should they successfully appeal a blocked sale. But she would also cast a narrower net than Feinstein, limiting prohibited purchasers to individuals whose names have been on the no-fly or “selectee” lists (allowed to board a plane, but designated for heightened screening), which are subsets of the larger consolidated terror watch list.

Ayotte is likely to cosponsor the Collins plan, and in the process gain a shield against Democratic attacks on her vote against expanded background checks. Sources with knowledge of Collins’ bill told Politico last week that they see Manchin and another moderate Democrat, Joe Donnelly of Indiana, as other possible backers of the measure.

The entry of a bipartisan terror gap bill into the mix could affect the calculus of Democratic leaders. Legislation that squeaked through the Senate would still have to get through the House, where Speaker Paul Ryan has said he’s in no hurry to push through a fix. “We’re going to take a deep breath and make sure that this is done correctly,” he said on Sunday on Meet the Press. The Collins plan would need Democratic support to pass — but forwarding a bill that the House might only squash would give away Democratic leverage in the bargain.

On Friday, an aide to Senator Harry Reid hinted at how the Minority Leader might size up any compromise effort that doesn’t enjoy the explicit blessing of Republican bosses and the NRA. Asked why Reid was dismissing the Toomey plan, the aide said that even if Senators reached a deal worth considering, “we don’t think” Senate Majority Leader Mitch McConnell “would ever allow a vote.”

According to aides in both parties, McConnell told Reid on Wednesday evening — hours from the filibuster’s end — that he would allow votes on amendments proposed by Democrats. But Murphy did not announce that offer until he wrapped up his filibuster around 2 a.m. Thursday morning.

Don Stewart, a spokesman for McConnell, told The Trace on Thursday that Republicans would have allowed the amendments to receive votes without the Democratic talkathon.

“It had literally no impact,” Stewart said.

Democrats counter that while McConnell may would not have allowed their universal background check bill onto the docket without public pressure.

“Just look the news,” said Chris Harris, a spokesman for Murphy. “They can’t claim that they weren’t obligated to do this.” (Over the course of the filibuster, the effort generated more than half a million tweets.)

On Friday, Delaware Senator Tom Carper took a different approach to using the federal government’s power to address the gun violence epidemic. He wrote a letter asking the Centers for Disease Control and Prevention to “prioritize existing funds to allow a more robust research” on gun violence.

For two decades, a congressional addendum known as the Dickey Amendment has mandated that “none of the funds made available for injury prevention and control at the CDC may be used to advocate or promote gun control.” With the CDC avoiding substantial gun violence research altogether in the years since, the congressional rider has come to be described by many Democrats, gun reform advocates, and reporters as an outright ban — and provided their coalition with a stick for bashing the NRA and the Republicans who do its bidding.

But as The Trace has reported, even under the restrictions of the Dickey Amendment, the CDC could be conducting more research into what the American Medical Association now calls a public health crisis. Calling the CDC out on that may weaken a popular anti-NRA talking point. But Carper, who could not be reached for comment, seemed to have other objectives.

“In the aftermath of the deadliest shooting in this nation’s history,” Carper said in a statement, “it would be the height of irresponsibility to do nothing to combat this gun violence epidemic.”

[Photo: Tom Williams/CQ Roll Call via AP Images]