Senate lawmakers will vote Monday on four measures aimed at controlling gun violence, including a measure that would allow federal officials to block people from purchasing firearms if they are under investigation.

The votes will happen in response to the Sunday terrorist attack in a Orlando gay nightclub that killed 49 people, plus the shooter, and injured 53 others, GOP leaders announced.

The shooter, Omar Mateen, had been on a terror watch list but was removed and was able to purchase two guns used in the shooting. The agreement comes after Sen. Chris Murphy, D-Conn., held the Senate floor for 15 hours with other Democrats in a push for stronger gun control legislation.

Sen. Dianne Feinstein, D-Calif., authored the terror watch list measure. It would allow federal investigators to block gun purchases by people who they are scrutinizing for possible links to terrorism.

The Senate will also vote on an alternative to Feinstein, sponsored by Sen. John Cornyn, that would put in place a three-day delay for gun purchases by people on the terror watch list. Cornyn's bill would require the federal government to prove in court that the purchaser should not own a weapon.

A third measure, sponsored by Sen. Chris Murphy, D-Conn., would require background checks at gun shows. Senators will also consider legislation sponsored by Sen. Charles Grassley, R-Iowa, that aims to increase prosecutions of people who try to illegally purchase guns, and ensure those will mental illness can't buy them.

Senators will vote on the measures as amendments to the fiscal 2017 Commerce, Justice, Science and related agencies spending bill.

But it may be difficult for any of them to pass. Republicans believe the Feinstein bill will violate the constitutional right to own guns, while Democrats have criticized the GOP bills as ineffective.

And while there may be majorities for some of these ideas, the Monday votes are votes to end debate on the proposals, which require a 60-vote supermajority, a steep hurdle given how split the two parties are between the proposals. If any do get 60 votes, the next step would be a vote to add them to the spending bill.

Republican have long been critical of expanding background checks, making it unlikely Murphy's bill will pass.

In the House, Republicans say they have no plans to take up legislation that would block people on the terror watch list from buying guns.

"We don't take away citizens' rights away without due process," House Speaker Paul Ryan, R-Wis., said Thursday when asked if he would consider the terror watch list gun legislation. "Again, I'm going to defend the Constitution here, we do not take away a citizen's rights without their due process. And so if you have a quick idea in the heat of a moment that says let's take away a person's rights away without their due process, we're going to stand up and defend the Constitution."