WASHINGTON - The national debate on gun laws came roaring back Thursday in the Senate, again putting Pennsylvania Republican Pat Toomey in the middle of a political storm.

Against the backdrop of Wednesday's shooting that killed 14 in San Bernardino, Calif., Democrats revived the bill to expand background checks that Toomey cosponsored in 2013, forcing a charged vote.

Democrats also pushed a vote on a plan to bar suspected terrorists on the federal government's no-fly list from buying guns.

Toomey quickly jumped on board with the background-check proposal - he cosponsored it, and was one of four Republicans to vote for it - but opposed the second measure, backing a less restrictive GOP version on terror suspects.

As expected, both proposals failed.

The point was not passage - the amendments were hitched to a bill to repeal the Affordable Care Act. That measure is doomed to a sure veto.

But Democrats hoped to draw a clear distinction on guns, and to spotlight senators from moderate states, such as Toomey, who could face difficult reelection fights next year.

"A husband shouldn't get a call that his wife was killed in the classroom because Republicans in Congress don't have the courage to challenge" the National Rifle Association, Sen. Charles E. Schumer of New York, the Senate's third-ranking Democrat, said at a news conference before the vote.

Toomey's contest is one of a handful that could determine control of the Senate.

His background-check bill, which he sponsored after the 2012 Sandy Hook school shooting in Connecticut and which was also blocked then, is a potent symbol of what he says is his willingness to work across the aisle.

It would expand the checks to cover more firearm sales, including those at gun shows, and has won him praise from some Democrats and advocates for tougher gun laws.

"If there's a sensible way to help keep the American people safer, I believe it deserves our support," Toomey said in a news release after the vote.

The measure failed, 48-50 - another reminder that new gun measures do not have the political support to become law.

Democrats have questioned Toomey's commitment to the issue, noting that since 2013 he has not reintroduced the bill himself and has rarely spoken about it.

Toomey's vote Thursday was prompted by his cosponsor, Sen. Joe Manchin (D., W.Va.), who brought the plan back for consideration amid a "vote-arama" - a series of rapid votes.

Toomey said he did not propose it himself so as not to cut in front of his colleague. He did not speak on the background-check proposal when it came up for a vote. Toomey has long said that he supports the bill but that he has not reintroduced it because he sees no realistic path to passage.

Democrats running to unseat Toomey accused him of hiding from his own measure.

Joe Sestak said in a release that either Toomey "lacked the courage" to bring his bill back on his own or "his true conviction remains the same as when he said 'my idea of gun control is a steady aim,' " citing a comment the senator made in 2010.

A spokeswoman for Katie McGinty, another of three Democrats running to challenge Toomey, accused the senator of "sitting on the sidelines" while his party controls the Senate.

The third Democrat, Braddock Mayor John Fetterman, pointed to Toomey's past votes to shield gun-makers from liability, decrease the waiting period for gun purchases, and block a proposal to ban high-capacity magazines.

"The NRA owns Pat Toomey," Fetterman said in a release.

A Toomey spokesman accused the Democrats of being motivated by "personal ambition."

The senator won praise Thursday from a gun-safety group, CeaseFirePA, which e-mailed supporters urging them to thank him "for standing firm in his support for this important measure." Such support could be critical among the swing voters who can tilt Pennsylvania elections - but Toomey also has to be wary of losing support from conservatives.

"If he does not change, he's guaranteed to lose this reelection," said Tom Campione, legislative director of Pennsylvanians for Self Protection, which has tried to dissuade Toomey from bringing his bill back.

Toomey helped stifle another Democratic initiative, voting against a proposal by Sen. Dianne Feinstein of California to bar anyone on the no-fly list from buying a gun.

"The bill is the definition of a no-brainer," Feinstein said. "If someone is too dangerous to board an aircraft, they're too dangerous to buy a gun."

But Republicans warned that some people end up on the watch list by mistake (the late Democratic Sen. Edward M. Kennedy among them) and could lose their Second Amendment rights through a government slipup.

The American Civil Liberties Union is among the groups that have criticized the no-fly list as ensnaring innocent people.

Feinstein's plan "provided no meaningful opportunity for innocent U.S. citizens to challenge being erroneously placed on a terrorist list," Toomey said in a statement.

He backed a Republican proposal that would allow the attorney general to delay a gun purchase by a suspected terrorist for 72 hours while seeking a court order to block the sale. Authorities would have to allow a hearing for anyone so stalled.

The sponsor, Sen. John Cornyn (R., Texas), said it would allow due process for gun buyers.

Senate Minority Leader Harry Reid (D., Nev.) said any lawyer could slow the process for 72 hours, potentially allowing a suspected terrorist to complete a purchase. "This is outrageous that people would try to run" from the Democratic plan, he said. "If you're on a terrorist watch list, you shouldn't be able to buy a gun."

jtamari@phillynews.com @JonathanTamari