“Barack Obama today launched the first attack ad from either campaign in this election, which follows a string of calculating position changes proving that Barack Obama’s commitment to a new type of politics is officially over. Even worse, Barack Obama actually voted for the Bush-Cheney energy bill and its big oil tax breaks that he is attacking, so let’s end the pretense that Obama is anything other than a typical politician.”
-- Tucker Bounds, a McCain spokesman.
Truth be told, I don't consider any of these ads to be "attack" ads, per se, although it was McCain who aired the first tough ad run by either candidate, with a validator implying that Obama was a Juan-come-lately to the concerns of Hispanic-Americans.
And then there's the ad that provoked the Obama response: an RNC independent expenditure spot drawing a contrast between Obama and McCain on energy.