The ads, from Kentuckians for Strong Leadership, will run from July 19 to July 26 and will attack Lundergan Grimes. It's the second such buy from the group in recent months, and it marks the early start of what's expected to be one of the nation's most expensive and hard-fought races of 2014.

The buy includes cable and broadcast television in the Louisville, Lexington, Bowling Green, Paducah and Evansville markets, as well as broadcast in the Hazard market. Buys in some of Kentucky's most populated areas are relatively cheap at this point, allowing the super-PAC to go on air early.

A Democratic super-PAC, Senate Majority PAC, went on air with a similar buy after the last round of the conservative group's ads went live, and indicated they're planning to match the attacks to defend Lundergan Grimes.

The Kentucky secretary of state announced her campaign earlier this month and has since laid low, making no public appearances, with a campaign launch planned on July 30.

McConnell and his allies, however, have kept up a steady stream of attacks on the Democrat since she announced.