Determined to turn Barack Obama’s celebrity into a liability, John McCain’s campaign is mockingly comparing the globe-trotting Democrat to Paris Hilton and Britney Spears.

Fleeting images of Hilton, famous primarily for being famous, and Spears, whose meltdowns have raised questions about her mental stability, are interspersed with those of Obama in a new TV ad unveiled Wednesday by the McCain camp. The ad features footage of 200,000 Germans chanting Obama’s name as a narrator intones: “He’s the biggest celebrity in the world. But is he ready to lead?”