Jack Conway isn’t going to win the Kentucky Senate race, but he will be remembered as the candidate with the single worst ad in the 2010 midterm cycle. How do we know? Well, it gave birth to one of the most effective counterpunches — a montage of liberal Democrats ripping Conway for attacking Rand Paul’s religious beliefs.

Howard Kurtz at his new Daily Beast perch observes that Conway’s is only the worst of a bad lot. It’s been an especially nasty season for Democratic ads:

We’re talking ugly stuff here …

“The party is doing stuff that is too hot for candidates,” says Evan Tracey, who tracks television advertising as president of the nonpartisan Campaign Media Analysis Group. “You see ad after ad going at them right between the eyes. It’s personal, it’s cutting. It’s ‘here’s what we found in the oppo dump and we’re going to put it in the worst light possible.’”

Kurtz provides a useful compendium of some of the more outlandish ones. He observes that the ads “represent the kind of scorched-earth tactics that strategists employ when their clients are in danger of losing, and losing big. The party is spending heavily on these aerial attacks.” Yes, negative ads sometimes “work,” but by going beyond the bounds of normal political combat, the candidates, like Conway, risk making themselves appear desperate and ethically challenged. And to the degree that independents hate partisanship, these ads are likely to be a major turnoff.

On the bright side, it does seem that the mainstream media and liberal punditocracy are embarrassed by all this. Alas, they had hoped for so much more from the Hope ‘n Change president.