It's becoming a steady drumbeat in the Kentucky Senate race: Trey Grayson attacks, and Rand Paul responds by tying him to President Obama. Now, though, it appears Bill Clinton is fair game too.

In what is shaping up to be one of the nastiest primaries in the country, Paul hit back with an ad for the second time this week.

More interesting about the latest Paul ad is that it points out Grayson voted for "draft-dodger Bill Clinton."

Grayson, a former Democrat, quipped at a GOP function last year that, “Some people in college tried pot; I tried Clinton.”