WASHINGTON — A Democratic senator who mourned the loss of 20 children in his home state of Connecticut waged a roughly 15-hour filibuster into the early hours Thursday, asserting as he yielded the floor that Republican leaders had committed to hold votes on expanded gun background checks and a ban on gun sales to suspected terrorists.

With a compromise on the gun issue still improbable, Sen. Chris Murphy stood on the Senate floor for most of Wednesday and into Thursday. Speaking in the wake of the mass shooting early Sunday at a Florida nightclub, Murphy said he would remain there “until we get some signal, some sign that we can come together.” He concluded the filibuster at 2:11 a.m., EDT.

Although Murphy talked optimistically about his cause, it is unlikely the amendments Democrats are seeking will pass the Republican-run Senate.

Murphy spent much of the time speaking about the shooting at Newtown, Connecticut’s Sandy Hook Elementary School in December 2012. He finished his filibuster by talking at length about one of the young boys who died there.

As Murphy had been standing on the floor for more than nine hours, his own young sons, ages 4 and 7, briefly appeared in the Senate gallery.

“I hope you’ll understand some day why we’re doing this,” Murphy said, addressing his oldest son from the floor. “Trying and trying and trying to do the right thing is ultimately just as important as getting the outcome in the end.”

Democrats have revived the gun debate after 49 people were killed at a nightclub in Orlando, the worst such incident in modern history. The fight pits strong proponents of the Second Amendment right to bear arms against those arguing for greater restrictions on the ability to obtain weapons.

Murphy’s call for the two votes came as presumptive Republican presidential candidate Donald Trump said he would meet with the National Rifle Association to discuss ways to block people on terrorism watch lists or no-fly lists from buying guns. The same day, Trump told a rally in Georgia: “I’m going to save your Second Amendment.”

Murphy was joined by more than 30 Democratic colleagues on the floor, many of whom angrily told stories of mass shootings in their own states and called for action.

“The next time someone uses a gun to kill one of us, a gun that we could have kept out of the hands of a terrorist, then members of this Congress will have blood on our hands,” said Massachusetts Sen. Elizabeth Warren.

Kirsten Gillibrand, D-N.Y., asked: “Where is our spine?”

Attempts at compromise appeared to collapse within hours of surfacing in the Senate Wednesday, underscoring the extreme difficulty of resolving the divisive issue five months from November’s election. Sen. Dianne Feinstein, D-Calif., who had been involved in talks with Sen. John Cornyn, R-Texas, said there was no resolution.

Murphy, 42, began speaking at 11:21 a.m., and was showing few signs of fatigue when the filibuster ended. By Senate rules, he had to stand at his desk the entire time to maintain control of the floor. When asked by another senator how he was feeling just before 7:30 p.m., Murphy said rehabilitation from a back injury in his 20s had helped him build up endurance.

Tourists and staff filled the galleries past midnight, and Democratic Sens. Richard Blumenthal of Connecticut and Cory Booker of New Jersey stayed with Murphy on the floor for most of the debate. Like Murphy, Booker did not sit down for the full 15 hours.

It’s been nearly a decade since Congress made any significant changes to federal gun laws. In April 2007, Congress passed a law to strengthen the instant background check system after a gunman at Virginia Tech who killed 32 people was able to purchase his weapons because his mental health history was not in the instant background check database.

Murphy is seeking a vote on legislation from Feinstein that would let the government bar sales of guns and explosives to people it suspects of being terrorists. Feinstein offered a similar version of the amendment in December, a day after an extremist couple killed 14 people in San Bernardino, California, but the Republican-run Senate rejected the proposal on a near party-line vote.

The Orlando shooter, Omar Mateen, was added to a government watch list of individuals known or suspected of being involved in terrorist activities in 2013, when he was investigated for inflammatory statements to co-workers. But he was pulled from that database when that investigation was closed 10 months later.

In a statement, the NRA reiterated its support for an alternate bill from Cornyn that would let the government delay firearms sales to suspected terrorists for up to 72 hours. Prosecutors would have to persuade a judge to block the transaction permanently, a bar Democrats and gun control activists say is too high.

Cornyn and other Republicans argue that Feinstein’s bill would deny due process to people who may be on the terror list erroneously.

In an attempt at compromise, Pennsylvania Sen. Pat Toomey introduced legislation that would direct the attorney general to create a new list of suspected terrorists who could be barred from buying weapons. But Democrats immediately rejected that idea, saying it would create too much of a backlog.

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Associated Press writers Erica Werner, Matthew Daly and Andrew Taylor in Washington, Jonathan Lemire in New York and Jill Colvin in Atlanta contributed to this report.