Sen. Chris Murphy Christopher (Chris) Scott MurphyMcConnell plans vote on Green New Deal before August recess Push to end U.S. support for Saudi war hits Senate setback Feehery: Defining what socialism is (and isn’t) MORE (D-Conn.) and other Democrats have taken over the Senate floor to call for tougher gun control laws and specifically action on keeping people on terrorist watchlists from buying firearms.

“I'm prepared to stand on this floor and talk about the need for this body to come together on keeping terrorists away from getting guns ... for, frankly, as long as I can, because I know that we can come together on this issue,” Murphy said in beginning the filibuster on Wednesday.

ADVERTISEMENT

Murphy began speaking at about 11:20 a.m., and the filibuster was still going more than 12 hours later.

Other Democrats who joined him included Sens. Richard Blumenthal (Conn.), Joe Manchin Joseph (Joe) ManchinThe Hill's Morning Report - Dems appear to have votes to counter Trump on emergency Border rebuke looms for Trump Trump claims Democrats ‘don’t mind executing babies after birth’ after blocked abortion bill MORE (W.Va.), Patrick Leahy Patrick Joseph LeahyDems introduce bills to restore Voting Rights Act provision Can Lindsey Graham take the politics out of judicial battles? Senate plots to avoid fall shutdown brawl MORE (Vt.), Al Franken Alan (Al) Stuart FrankenVirginia can be better than this Harris off to best start among Dems in race, say strategists, donors Virginia scandals pit Democrats against themselves and their message MORE (Minn.), Cory Booker (N.J.), Bill Nelson Clarence (Bill) William Nelson2020 party politics in Puerto Rico There is no winning without Latinos as part of your coalition Dem 2020 candidates court Puerto Rico as long nomination contest looms MORE (Fla.), Dick Durbin Richard (Dick) Joseph DurbinKids confront Feinstein over Green New Deal Senate plots to avoid fall shutdown brawl Overnight Energy: Trump ends talks with California on car emissions | Dems face tough vote on Green New Deal | Climate PAC backing Inslee in possible 2020 run MORE (Ill.), Charles Schumer Charles (Chuck) Ellis SchumerBrady gun control group gets rebranding Brennan fires back at 'selfish' Trump over Harry Reid criticism Trump rips Harry Reid for 'failed career' after ex-Dem leader slams him in interview MORE (N.Y.), Ben Cardin Benjamin (Ben) Louis CardinClyburn pushes next steps on criminal justice reform The Hill's Morning Report - Dems appear to have votes to counter Trump on emergency The Hill's 12:30 Report: Trump looks for boost from Korea summit MORE (Md.) and Ed Markey Edward (Ed) John MarkeySenate Dems seek to turn tables on GOP in climate change fight Ocasio-Cortez responds to Ivanka Trump: 'I actually worked for tips and hourly wages' Overnight Energy: McConnell plans Green New Deal vote before August recess | EPA official grilled over enforcement numbers | Green group challenges Trump over Utah pipelines MORE (Mass.).

It also won support from presumptive Democatic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonREAD: Cohen testimony alleges Trump knew Stone talked with WikiLeaks about DNC emails County GOP in Minnesota shares image comparing Sanders to Hitler Holder: 'Time to make the Electoral College a vestige of the past' MORE and her rival, Sen. Bernie Sanders Bernard (Bernie) SandersSenate Dems seek to turn tables on GOP in climate change fight Bernie Sanders Town Hall finishes third in cable news race, draws 1.4 million viewers Woman to undecided Biden: 'Just say yes' to 2020 bid MORE (I-Vt.).

Some fights are too important to stay silent. Preventing gun violence is one of them. Stand strong @ChrisMurphyCT. https://t.co/LEl7iSLCgF — Hillary Clinton (@HillaryClinton) June 15, 2016

The Senate is currently considering an appropriations bill for the Commerce and Justice departments and science programs. Though no votes are currently scheduled, the senators are blocking any amendments to the bill.

"I don't think we should proceed with debate on amendments to this bill until we have figured out a way to come together," Murphy said, referring to the spending bill.

The Democrats are also technically blocking Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellWhite House pleads with Senate GOP on emergency declaration Senate Dems seek to turn tables on GOP in climate change fight Pence meets with Senate GOP for 'robust' discussion on Trump declaration MORE (R-Ky.) from ending debate on the legislation, though a spokesman shot down any speculation that the Republican leader would have tried to wrap up work on the spending bill Wednesday.

Democrats have given no indication how long they plan to hold the Senate floor. Chris Harris, a spokesman for Murphy, said Democrats launched the talkathon because the senator will no longer accept “inaction or half measures in the face of continued slaughter.”

The effort comes three days after the deadliest mass shooting in U.S. history. A gunman armed with a Sig Sauer MCX rifle and a handgun on early Sunday killed 49 people at an Orlando nightclub.

Murphy is well-known for his support for tougher gun control laws. One of America's most shocking gun crimes occurred in his home state in Newtown, where 20 children and six adults were shot to death at Sandy Hook Elementary School.

"I can't tell you how hard it is to look into the eyes of the families of those little boys and girls who were killed in Sandy Hook and tell them that almost four years later we've done nothing, nothing at all," Murphy said.

Since the Orlando attack, Democrats have put a renewed focused on legislation meant to block the sale of guns to people on terrorist watchlists.

An effort to move legislation was previously blocked last year.

Sen. Ben Sasse (Neb.) was the first Republican senator to join Murphy and other Democrats, asking a question about the government's terror watchlists.

"I'm familiar with the terrorist screening database. There are a series of lists that fall from the database, but I don't think there's any such thing as 'the terrorist watchlist,' and I certainly don't understand what due process rights would apply," Sasse said.

Sasse's comment reflects a central problem Republicans have with a proposal from Sen. Dianne Feinstein Dianne Emiel FeinsteinSenate confirms Trump court pick despite missing two 'blue slips' Hillicon Valley: Senators urge Trump to bar Huawei products from electric grid | Ex-security officials condemn Trump emergency declaration | New malicious cyber tool found | Facebook faces questions on treatment of moderators Ocasio-Cortez adviser says Sunrise confrontation with 'old-timer' Feinstein 'sad' MORE (D-Calif.) that would give the attorney general broad authority to block people on watchlists from being able to buy guns or explosives.

Republicans argue that could deny constitutional rights to Americans who aren’t actually tied to terrorism.

Instead, Sasse and most Republicans support an alternative proposal by Sen. John Cornyn John CornynGOP lawmaker says panel to investigate drug company gaming of patent system Senators grill drug execs over high prices Cornyn less popular than Cruz in Texas: poll MORE (R-Texas) that would allow the attorney general to delay suspected terrorists from getting a gun for up to 72 hours while seeking a court order to stop the sale.

Sen. Pat Toomey (R-Pa.), who faces a tough reelection bid, came to the Senate floor urging his colleagues to compromise.

"There's an obvious opportunity here, guys, to work together and find the solution," he said. "What I'm suggesting is let's get to work here."

Toomey on Wednesday criticized the Feinstein measure as "badly flawed." But he also said that Cornyn's proposal, which he previously voted for, likely didn't give enough leeway to the attorney general.

He made the comments after Democratic Senate candidate Katie McGinty, who is hoping to unseat Toomey, pressured the GOP senator to back the Feinstein legislation during a press conference Tuesday.

Wednesday afternoon, Toomey said he planned to introduce a compromise bill Thursday aimed at combining aspects of both the Feinstein and Cornyn proposals.

Toomey's legislation would require the attorney general to create a list of "likely terrorists" that could be blocked from buying guns. The list would then be submitted to the Foreign Intelligence Surveillance Court, which would review it annually and remove any Americans inadvertently included, according to a summary of the forthcoming bill from his office.

Updated at 11:35 p.m.