It's hard to see a former congressional candidate who hasn't held office putting up a strong challenge against the Senate Minority Leader, but the timing of Marksberry's announcement is significant: it came the day after a poll pegged McConnell as the least-popular senator in the nation.

That same poll, however, still put him ahead of every Democratic challenger tested, including actress Ashley Judd, who is rumored to be considering a bid. And Mitt Romney won the state with over 60 percent of the vote, indicating any Democratic challenger will be a tough sell in the increasingly red state.

Watch Marksberry's announcement: