The political action committee founded by former Democratic Rep. Gabrielle Giffords of Arizona endorsed Republican Sens. Patrick J. Toomey and Mark S. Kirk in their re-election efforts.Americans for Responsible Solutions, which backs candidates who support gun control, endorsed Toomey, who is running for re-election in Pennsylvania against Democrat Katie McGinty. Toomey worked with West Virginia Democrat Joe Manchin III on Senate legislation to improve background checks.

The endorsement comes after Toomey also received support from former New York Mayor Michael Bloomberg’s group Independence USA. That group released an ad featuring the daughter of the principal killed in the Sandy Hook Elementary School shooting in Newtown, Connecticut, in 2012 along with 20 students and five teachers.

Kirk is locked in a tough re-election fight against Democratic Rep. Tammy Duckworth in Illinois.

[Gun Control Meets Congressional Dysfunction]

Giffords praised both senators for supporting the background check legislation in an op-ed on CNN.com written with her husband, astronaut Mark Kelly. She also added that the endorsements weren’t easy to make.

“With so many more candidates running on a gun violence prevention platform, in some places the changing politics of gun safety has made our endorsement decision difficult,” she wrote.

Giffords described McGinty as a “passionate advocate for gun violence prevention,” and lauded Duckworth for being “a champion for commensense gun laws in the House.” She said both candidates would support gun safety laws if elected to the Senate.  

The Arizona Democrat became an advocate for gun control measures after she was shot in 2011 at a campaign event in Tucson, which ultimately led to her resignation from Congress. Six people were killed in the mass shooting attack.

Kirk said in a statement that he was grateful for the group’s support.

“The only way to break through the partisan gridlock in D.C. is by working across the aisle to reach bipartisan solutions,” he said. “And I remain committed to working with Republicans and Democrats alike to get the job done and end the cycle of gun violence.”