Advocates for stricter gun laws have singled out four Republican senators, including Majority Leader Mitch McConnell (Ky.), in an aggressive ad campaign to urge congressional action on new gun control policy.

The ads, which also call out Sens. Cory Gardner (Colo.), Marco Rubio (Fla.) and Rick Scott (Fla.), begin with a montage of news footage from some of the nation’s worst mass shootings of the past decade. A voice-over then urges the senators to “stand up to the gun lobby and pass bipartisan background check and red flag laws.”

The group behind the ads, Everytown for Gun Safety Action Fund, is spending $350,000 on these television spots, which will run on national morning news shows as well as local broadcasts in the senators’ respective states. The Rubio ad will also air in Spanish.

The focus on these four senators appears both political and personal. McConnell and Gardner will be up for reelection in 2020. Gardner’s home state of Colorado has endured two decades of mass shootings, including attacks in which at least a dozen people died, at Columbine High School in 1999, a movie theater in Aurora in 2012 and STEM School Highlands Ranch this year.

Although neither Rubio nor Scott will face voters for several years, the 2018 shooting massacre at Marjory Stoneman Douglas High School in Parkland, Fla., began a new era in gun-control advocacy. Scott was Florida’s governor then and signed new red flag laws, which allow law enforcement officials to have weapons confiscated from a person who is deemed a risk to themselves or others.

McConnell and other congressional Republicans expressed an openness to some kind of gun safety legislation in the wake of back-to-back mass shootings in El Paso and Dayton, Ohio, earlier this month, but have not committed to anything specific.

President Trump has sent mixed signals to Capitol Hill about how committed he is to doing something about the nation’s gun violence.

Rubio, after presiding over the Senate’s pro forma session on Tuesday, told reporters that he supports red flag laws, but remained noncommittal on closing loopholes in background checks for firearm purchases.

The senator said there were “hundreds of occasions” where law enforcement in his state was able “to go to the courts and prove that someone’s dangerous and potentially prevent them either taking their own life, or someone else’s.”

Rubio sponsored a red flag law bill earlier this year, but now there are several versions.

“Either way, we just want one to pass,” Rubio said.

Meanwhile, House Judiciary Committee members are returning to Washington from their summer recess a week early to vote on three gun control measures. On Sept. 4, they’ll take up a bill that would limit high-capacity ammunition magazines, one to implement red flag legislation and another to keep guns out of the hands of people convicted of misdemeanor hate crimes.

Mike DeBonis contributed to this story.