New York City Mayor Michael Bloomberg’s gun-control group is following through with its pledge to air ads against Arkansas Sen. Mark Pryor, who Democrats see as one of their most vulnerable incumbents in a tough 2014 climate.

A source tracking media spending told POLITICO the group has bought $350,000 worth of broadcast and cable air time starting Friday and running through June 6, a crushing amount in a state where ad time is fairly cheap…

Democrats have been concerned about their members being hammered by Bloomberg’s group and other gun-control activists after legislation backed by the White House to expand background checks, among other measures, failed in the Senate.