In a presidential campaign freighted with war, recession and energy woes, a jibe featuring Paris Hilton, of all things, seems to have struck a nerve in Democrat Barack Obama. For the second time in two weeks, he aired a TV ad Monday rebutting Republican John McCain’s claim that Obama is little more than a celebrity, like the blonde hotel heiress.

The first time, Obama dismissed the assertion as “baloney.” On Monday, Obama took a different tack with a commercial that says McCain, not he, is “Washington’s biggest celebrity.”

They woke up this weekend and figured out that that ad resonated and they needed to do something about it,” said Terry Holt, a Republican strategist.

Although the McCain campaign was lampooned for its Hilton ad on late night television and blogs, it kept hammering at the celebrity theme. A McCain TV ad introduced last week showed Obama waving to cheering crowds, along with his picture on the covers of the magazines GQ, US Weekly and Vanity Fair.

In his new ad, Obama tries to turn the celebrity theme to his advantage, grafting it to his claim that a McCain presidency would amount to a third term for Bush.

Holt, the GOP strategist, said, “If the celebrity issue were not hurting them, they would have ignored it.”