One day after Republican presidential hopeful John McCain released an ad comparing Barack Obama to Britney Spears and Paris Hilton, Obama shot back with his own ad criticizing McCain's persistent "attacks."  

Obama was diplomatic yesterday when he put the kibosh on McCain's ad, telling MSNBC, "I don't pay attention to what McCain says." When asked about the ad, Obama said, "although I do notice that he doesn't seem to have anything very positive to say about himself, does he?"

So what does Britney have to say? When ET contacted her record label today, we were told "No Comment."