Three days after 49 people were killed at a nightclub in Orlando, Florida, in what marks the worst mass shooting in modern U.S. history, Connecticut Democratic Senator Chris Murphy started a filibuster to force a vote on a gun control bill.

At about midnight on Wednesday, 12 hours after Sen. Murphy said he would remain on the Senate floor “until we get some signal, some sign that we can come together” on letting the government prohibit sales of guns and explosives to people it suspects of being terrorists, he noted, with great curiosity, how his office with its limited resources was able to field 10,000 calls urging him and like-minded senators to carry on the fight to force a vote on legislation by Sen. Dianne Feinstein of California first offered in December, a day after an extremist couple killed 14 people in San Bernardino, California.

Sen. Feinstein’s amendment was rejected by a Republican-controlled Senate along a near party-line vote. Sen. Murphy also wants an an expansion of background checks.

“For those of us that represent Connecticut, the failure of this body to do anything, anything at all in the face of that continued slaughter isn’t just painful to us, it’s unconscionable,” Murphy said, the AP reported.

After almost 15 hours holding the Senate floor, GOP leadership agreed to allow s vote on gun control legislation. Democrats claimed victory, but that victory will probably be short-lived because any bill passed in the Senate will have to face worse odds in the GOP controlled House of Representatives. Senate Majority Leader Mitch McConnell will allow votes on amendments seeking to tighten the nation’s gun lawsto an annual appropriations bil on a Commerce, Justice, Science appropriations bill, the New York Times reported Thursday.

Portman Not With Murphy, Brown

Among the 40 senators taking the floor to back Sen. Murphy was Ohio’s senior U.S. Senator Sherrod Brown. Earlier Wednesday, during his regular Wednesday conference call with Ohio reporters, Sen. Brown said, “It’s outrageous for this senate and this congress not to stand up to the gun lobby.” Republicans have stood with the gun lobby, he said, even though the FBI thinks someone on a terrorist no-fly list shouldn’t be able to buy an assault weapon.

Sen. Brown spent his time on the floor reading two letters from people in Ohio who want tougher gun laws. The two-term senator has called on the Senate to stay in session and do its job, including holding hearings on President Obama’s nomination of Merrick Garland for the Supreme Court, instead of leaving Washington.

Ohio’s junior Senator, Rob Portman, one of several endangered GOP senators who could return control of the upper chamber to Democrats next year if he loses his reelection, is in the line of fire on the issue because it seems he wants to be on both sides of the issue.

Tweeted today by New York Times reporter , a Portman aide said the senator’s “position on restricting gun sales to terror suspects unchanged-He still backs Cornyn measure, opposes Feinstein.” 

Democrats and Sen. Portman’s chief challenger, former Ohio governor Ted Strickland, pounced on what was cast as gun-control stance flip-flop.

Ohio Democratic Party spokesman Daniel van Hoogstraten said via email, “In less than 24 hours, Senator Portman tried to lie about his record of voting against banning terrorists from buying weapons, got caught, claimed he changed his position, and now has flip-flopped again.” According to Mr. van Hoogstraten, the facts are that Sen. Portman voted just last year against banning terrorists from buying weapons.

Ted Strickland was quick to point out that Ohio voters will have the final say later this year. “To them and to Senator Portman, I say: can you look in the mirror today and say you have done everything possible to prevent the terrible tragedy that occurred in Orlando on Sunday? If your answer is yes, then that is between you and your conscience. Ohio voters will offer their own judgment at the ballot box.” Sen. Portman and Mr. Strickland are in a dead-heat race.

Ohio newspapers have written about Sen. Portman’s record of opposing banning gun sales to suspected terrorists. The Dayton Daily News reported on Sen. Portman’s opposition to the Feinstein bill allowing the U.S. Attorney General to block the sale or transfer of a gun or explosive to a suspected or known terrorist.

“Portman initially maintained that the Feinstein amendment only applied to the federal no-fly list – a smaller list of people and had no due-process provisions. But after checking with an aide, the senator yielded that ‘maybe we had this wrong,’” posted.

In spite of expected resistance from Republicans, Democrats are renewing their drive since the Sunday morning shooting in Orlando for gun control legislation. Congress passed a law in April 2007 to strengthen the instant background check system after a gunman at Virginia Tech was able to purchase his weapons because his mental health history was not in the instant background check database, the AP reported today.

Vice President Joe Biden said today that it took him seven years to win passage of the first assault weapons ban in the mid-1990s that ended after 10 years, in 2004, under President George W. Bush. “We should not stop” pushing for new laws,” the vice president said at Mellon Auditorium in Washington to parents of children killed by a deranged gunman n Newtown, Connecticut in 2012. CNN reported Mr. Biden commented on the resistance to reduce gun violence, saying, “This borders on irrational.”