American Future Fund has now spent over $1 million defending Sen. Kelly Ayotte (R-N.H.), thanks to a new $452, 000 ad buy in New Hampshire and Boston.

The buy is part of an ongoing air war over Ayotte's opposition to expanded background checks for gun buyers. Ayotte was the only senator in the Northeast to vote against the legislation, and both supporters and opponents of gun control see New Hampshire as a testing ground for their power going forward.

Mayors Against Illegal Guns, a group backed by New York City Mayor Michael Bloomberg, has spent an estimated $650,000 in the state against the senator. Americans for Responsible Solutions, the group founded by former congressman Gabrielle Giffords, has spent about $350,000 on radio ads criticizing her vote.

The American Future Fund ad pushes back on those spots, calling them "flat-out wrong... partisan deliberately misleading." Ayotte, the ad says, voted for "fixing background checks" and "common-sense gun reforms." Ayotte supported a Republican alternative gun bill, sponsored by Sens. Ted Cruz (R-Texas) and Chuck Grassley (R-Iowa), that would have cracked down on background check violations but did not expand the system.

American Future Fund, a 501(c)(4) social welfare organization with ties to Iowa Republicans, first gained national prominence in the 2010 election.