The bar going into tonight seemed to be double-digits...if Obama won by double-digits, he could claim a clear victory. If Clinton had kept his margin to single-digits, her campaign could have claimed a moral victory. Right now, with 85% of the precincts in, Obama is up 58-41%, showing that he exceeded expectations yet again. This may be the most striking thing about the (soon to be) 10 state winning streak...in most of these contests he hasn't just won, he has won big, and exceeded expectations at every turn.
One interesting note is that the composition of the Democratic electorate was almost exactly as it was in 2004. According to exit polls, 9% of those voting in the Democratic primary were Republicans, 28% were independents, and 62% were Democrats. The high turnout among independents and Republicans helped Obama widen his margin of victory, but he even won Democrats 53-46%.
Obama's margin was also wider than what the polls predicted, something that we also saw in last week's primaries. As a result, rather than taking a net gain of 6 delegates from Wisconsin (which is the estimate I generated based on the polls) he will likely take a net 12 delegate advantage from the state.
As has already been widely reported, Obama won white men 63-34% and white women went only very narrowly for Clinton (52-47%). Obama also won union households by about 10%, perhaps helped by his recent union endorsements. He won nearly every demographic except, as the commentators kept pointing out mercilessly, Clinton carried old white women.