You didn't think he was going to campaign as George McGovern, did you?
Naturally, his base is freaking out, but let's face it, they're not going anywhere.
Of course there's nothing much new in what the senator has done. In the lexicon of modern American politics, it's called a pivot. You campaign hard to the party's extreme in the primary election, where the base voters tend to be. Then, when the nomination is secure and there are no more idealists to be humoured, you pivot back to the centre. The only difference is that in Mr Obama's case the pivot is so hard and so fast that the entire Democratic Party is suffering from whiplash.The latest supporters to be tossed under the bus are the anti-war crowd. Sorry folks, he's not listening any more.
A whimper of pain has gone up from the base. Those who really believed in the Audacity of Hope now fear a Timidity of Despair. Thousands of Obama supporters have signed a petition on his website begging him to reconsider his position on the illegal wiretaps - a seemingly minor campaign issue, but one that carries great talismanic symbolism for civil libertarians.
Left-wing commentators have raised the usual cry of betrayal. Arianna Huffington, that rare creature, a young conservative who moved sharply left in middle age, dubbed Mr Obama's move not realpolitik, but “realstupidpolitik”.
Conservatives, meanwhile, led by John McCain's Republican campaign, say that the presumptive Democratic nominee's pivot shows that, for all his talk of offering a new kind of politics, he is really just another cynical politician who will say anything to get elected.
I suspect that all this worries Mr Obama not at all. The louder the Left complains, the deeper the satisfaction at Obama headquarters.