Few people would associate Barack Obama with Britney Spears or Paris Hilton – America’s blondest and least political of celebrities. But thanks to the latest campaign advertisement from John McCain that link has now been established.

“He is the biggest celebrity in the world,” says the narrator against a picture of Mr Obama speaking to 200,000 people in Berlin, which then cuts to images of Ms Spears and Ms Hilton. “But is he ready to lead?”