The ad, a "positive spot," according to the aide, will air in the Lexington and Louisville, Ky. media markets for a week. The campaign is also launching a radio ad.

The early launch has been seen by some Democrats as a signal McConnell is concerned at his reelection prospects nearly two years from now. And recent polling, which shows him to be the nation's least popular Senator, supports their assertion that he's a top pickup opportunity for Democrats in 2014.

But McConnell has over $7 million cash on hand, and is actively fundraising for what his aides say they expect to be a tough fight.

Actress Ashley Judd and Secretary of State Allison Lundergan Grimes are both contemplating launching a challenge, though neither has yet made their decision official.