Pryor defends gun-control opposition in first ad

"The mayor of New York City is running ads against me because I oppose Obama's gun-control legislation. Nothing in the Obama plan would have prevented tragedies like Newtown, Aurora, Tucson or even Jonesboro," he says in the ad.

Pryor has become the subject of a series of negative ads from the pro-gun-control group Mayors Against Illegal Guns, which is backed by New York Mayor Michael Bloomberg, because of his vote against the Toomey-Manchin background checks bill.

In his new ad, he distances himself from both Bloomberg and President Obama, and frames himself as an independent fighter for Arkansas — the argument he'll have to win to keep his seat in what will be a difficult fight in 2014.

"I'm Mark Pryor and I approve this message because no one from New York or Washington tells me what to do. I listen to Arkansas," he says.

That fight has begun unusually early, with Pryor going on air this Friday, nearly a year and a half out from Election Day.

That's partly because he faces attacks from both the left and the right: A conservative group, Senate Conservatives Fund, has labeled him their top target for 2014, and the conservative Club for Growth has already targeted him with ads as well. Republicans see his seat as one of their top pickup opportunities in 2014, as Mitt Romney won Arkansas by more than 20 percentage points.