New Nelson attack ads blast Mack's 'history of barroom brawls, altercations, and road rage'

The ad goes on to accuse Mack of having left "a trail of debt, liens and unpaid bills." The commercial also knocks Mack's 2012 House attendance record — sparse because of time the Florida lawmaker spent campaigning for Mitt Romney — and for voting "to end Medicare as we know it" — an apparent allusion to House Budget Committee Chairman Paul Ryan's (R-Wis.) proposed budget.

“Questionable work habits. A sense of entitlement. Connie Mack: he thinks the rules are different for him," the ad concludes.

The tough attack ad is the opening salvo in what looks to be an increasingly nasty campaign. According to the Miami Herald, outside conservative groups have already spent $7 million in the state attacking the incumbent Nelson. Mack is favored to win the GOP nomination when Florida holds its primary on Aug. 14.

But despite having posted early leads over Mack as the Republican congressman struggled through the GOP primary, the race now seems poised for a down-to-the-wire finish. A poll released Wednesday by Democratic polling firm Public Policy Polling found Nelson holding a mere two-point lead. Of those surveyed, 45 percent backed the Democratic senator and 43 percent backed Mack.