(AP) -- Among the Senate's most vulnerable Republicans, Pennsylvania Sen. Pat Toomey stood firmly with the powerful National Rifle Association on the latest ill-fated attempts at gun control. So did Ohio Sen. Rob Portman and Wisconsin Sen. Ron Johnson.

Not so Illinois Sen. Mark Kirk, who represents Chicago where so far this year, more than 1,780 people have been shot, leading to the vast majority of the city's 294 homicides, according to police.

Just over four months to the election, and facing pressure from their Democratic opponents, most Republican Senate incumbents opted for consistency despite the political frenzy days after the worst mass shooting in modern American history. A lone gunman, Omar Mateen, killed 49 people and injured 53 at a nightclub in Orlando, Florida, prompting fresh calls for tighter restrictions on weapons. Mateen had been the focus of two terror investigations that were dropped.

Toomey, Portman and Johnson -- as they did in December after shootings in San Bernardino, California -- supported a NRA-preferred measure to deny a gun sale to a known or suspected terrorist, but only if prosecutors could convince a judge within three days that the would-be buyer was involved in terrorism. The three also helped to defeat a Democratic-sponsored bill to close the gun show loophole and expand background checks.

In the end, four amendments -- two Democratic and two Republican -- failed in a deeply divided Senate.

White House spokesman Josh Earnest, appearing on CNN Tuesday, denounced the votes as "a shameful display of cowardice."

In turn, Chris W. Cox, executive director of the National Rifle Association Institute for Legislative Action, called the votes "embarrassing" and said "the safety of the American people is taking a back seat to political theater."

Kirk, facing a strong challenge from Democratic Rep. Tammy Duckworth, supported the Democratic background checks bill and another Democratic measure to allow the government to deny gun sales to suspected terrorists.

The lone reversal was Sen. Kelly Ayotte of New Hampshire, who is in a tight re-election bid against Democratic Gov. Maggie Hassan. Ayotte supported both the Democratic and Republican versions of the amendments to deny gun sales to suspected terrorists.

Ayotte said she is working with Maine Sen. Susan Collins, a moderate Republican, on possible compromise legislation.

"To get to that solution, we have to move this debate forward," Ayotte said on the Senate floor, defending her votes.

Democrats immediately pounced.

"She should make up her mind and not be a hypocrite," said Senate Democratic Leader Harry Reid.

New Hampshire is home to some of the nation's most lenient gun laws, but Ayotte's approval rating fell after she voted against expanding background checks following the 2012 shooting at a Newtown, Connecticut elementary school.

In April 2013, the daughter of one of the Newtown victims confronted Ayotte at a town hall.

"You had mentioned that the burden to owners of gun stores that these expanded checks would cause. I'm just wondering why the burden of my mother being gunned down in the hall of her elementary school isn't as important as that?" asked Erica Lafferty Smegielski, whose mother, Dawn Hochsprung, was the principal at Sandy Hook Elementary School.

Smegielski was in the hallway outside the Senate during the votes Monday, and pledged to continue the pressure.

"My next step is to take a tally of who voted where and bring it to the polls in November," she said.

Florida Democrats have targeted Republican Sen. Marco Rubio, who is considering a run for re-election after previously saying he would give up his seat. Rubio defended his votes against the Democratic measures, saying they were "politically motivated and driven by a larger ideological agenda to disarm Americans."

Democratic Rep. Patrick Murphy, who is running for Rubio's seat, shot back at Rubio, saying he "put his political ambition ahead of keeping Floridians safe."

In Pennsylvania, Katie McGinty, Toomey's Democratic challenger, immediately criticized the Republican's votes. She said the senator is "long on rhetoric but short on action."

Toomey had attempted to craft his own compromise last week to deny gun sales to terrorism suspects. In a speech on the floor Monday, he pushed for votes on either his own compromise or Collins' bill.

"We're talking past each other," Toomey said of the multiple failed amendments.

Johnson appeared less concerned. He declined to discuss his votes with reporters before the vote.

"I'm not worried about it all," he said of the gun issue and his tough re-election bid against former Democratic Sen. Russ Feingold.

Some Democrats also took tough votes. Democratic Sens. Heidi Heitkamp of North Dakota and Jon Tester of Montana voted against expanded background checks, while Indiana Sen. Joe Donnelly voted for both the Republican and Democratic amendments. All three are up for re-election in heavily Republican states in 2018.