So what is the meaning of last night? I hesitate to draw many conclusions, because I'm often wrong about these things, but I think it's fairly safe to say that McCain was the big loser last night. Here, he's just become the presumptive nominee of the Republican Party, and he loses two states, one by a large margin and only ekes out a small plurality in the third, with over seventy percent of the people voting against him -- even for two candidates who are no longer running and a third ("uncommitted") who isn't even a person. I doubt that bodes well for his general election chances, but we still have a long way to go. Just remember that only one year before he lost his re-election bid, George H.W. Bush looked like a shoe-in to win in a landslide.
I think it's also fair to say that, while not devastating, last night was not friendly to Hillary. Can Obama pick up some new momentum from that? I don't know. It probably depends on how the press plays it and on how things turn out in Maine today.