The gun lobby may have abandoned Sen. Mark Pryor (D-Ark.) and Sen. Mark Begich (D-Alaska), even though both senators voted against a universal background checks bill last year. But groups focused on reducing gun violence are sticking to their pledge to help re-elect lawmakers who voted for the measure.

Americans for Responsible Solutions PAC, the political arm of former Rep. Gabby Giffords' (D-Ariz.) anti-gun violence group, released a new television ad Tuesday in support of Sen. Susan Collins, who is up for re-election in Maine. Collins was one of just four Republicans who voted for a Senate bill that would have expanded background checks in the wake of the 2012 massacre at Sandy Hook Elementary School in Newtown, Connecticut.

The new ad, "Steady for Maine," is part of a six-figure buy and will air for at least two weeks on broadcast and cable. It refers to Collins as "a calm voice in a sea of shouters" for her tendency to reach across the aisle, and highlights her vote to advance the background checks compromise, which the narrator points out would have kept guns "out of the hands of the dangerously mentally ill and domestic abusers." (Watch the ad above.)

When announcing its priorities for the 2014 midterm elections earlier this year, ARS included Collins in a list of lawmakers to whom it would lend its resources in the months leading up to November. Collins is comfortably ahead of her Democratic opponent, Shenna Bellows, in the polls. Bellows has also expressed her support for universal background checks.

Hayley Zachary, executive director of Americans for Responsible Solutions, said Collins was "a steady, bipartisan voice for commonsense solutions to reduce gun violence."

"In the face of powerful special interests, Senator Collins stood up for reasonable policies that will make our communities safer," Zachary said. "We need more people like Susan Collins in the United States Senate."

ARS is also helping Democratic Sens. Mark Udall (Colo.), Mary Landrieu (La.), Jeanne Shaheen (N.H.), Kay Hagan (N.C.) and Al Franken (Minn.) in their re-election battles, among other candidates who have expressed support for expanding background checks. Last month, Everytown for Gun Safety, the group launched by former New York City Mayor Michael Bloomberg, also announced plans to support candidates from both parties who either voted for or support universal background checks.

By contrast, the National Rifle Association has not rewarded Pryor and Begich, even though the two Democrats helped defeat the background checks bill by joining a GOP-led filibuster against it.

The NRA declined to make an endorsement in the Alaska Senate race, where Begich is currently trailing his GOP challenger Dan Sullivan.

In Arkansas, the NRA went a step further and announced a $1.3 million ad buy endorsing Rep. Tom Cotton, Pryor's Republican opponent. The NRA's ad made no mention of Pryor but said that Cotton will stand up to President Barack Obama's "extreme" gun agenda.

The NRA appears to be turning its back on Pryor even though the group ran radio ads defending the Arkansas Democrat after his background checks vote last year. At the time, the NRA said it was not committing to supporting Pryor in his re-election campaign.

Cotton currently holds a slim lead over Pryor, according to HuffPost's Pollster average.