It’s what happened when McCain unleashed his endless barrage of negative ads against Obama; it hurt McCain, not Obama. And it’s very good to note that the same happened to Liddy Dole:
Anzalone said that the high-profile attack ad doomed Dole’s chances to keep the race close. Hagan’s internal polling showed her numbers skyrocketing after the ad aired. "It would have been a much closer race [if she didn’t air the Godless ad]. Kay would have won by 3-4 points but instead she won big," Anzalone said. "I just think Dole, in the end, did herself a disservice. She was going to lose that race, but she did not need to lose that race by that margin."
The Dish 