Mayors Against Illegal Guns, the pro-gun control group backed by New York City Mayor Michael Bloomberg, is not giving up the fight.

Three weeks after the Senate rejected legislation offered in the wake of the December shooting massacre that left 26 people dead at a Connecticut elementary school, the group is launching what appears to be a high-priced ad campaign to keep the pressure on lawmakers.

The ad attacks Sen. Kelly Ayotte, a New Hampshire Republican who was the lone lawmaker from the Northeast to vote against the gun control measure; another advertisement praises Sen. Pat Toomey, a Pennsylvania Republican who helped craft failed compromise bill, but urges voters to keep the pressure on by calling him to declare their support for universal background checks for gun buyers.

Both ads appeared today on Ad Hawk, Sunlight's tool for tracking political advertising on television. Meanwhile, Political Ad Sleuth, Sunlight's tracker for  political ad purchases, shows a large buy at one of the Boston TV stations that broadcasts into New Hampshire: $138,000 for 88 spots to air over the next two weeks on WCVB.

The Sunlight Foundation is a nonprofit, nonpartisan organization that uses the power of the Internet to catalyze greater government openness and transparency, and provides new tools and resources for media and citizens, alike. A list of Sunlight's funders can be found here.