I think pollsters and experts were right that most of the independents in New Hampshire (45% of all voters) liked two candidates: Obama and McCain. In the forty-eight hours before the polls closed, they got a consistent message about their two favorites: Obama had his victory in the bag, but McCain was potentially in trouble. Therefore, sophisticated independent voters (who could choose to participate in either the Republican or Democratic contest) reasoned that McCain needed their help but Obama didn’t. Therefore, those who wanted, above all, to make a difference, switched at the last moment to the GOP side, abandoning their previous intention to vote Democratic. That’s why the split of independent voters between those who went with the GOP and those who went with the Democrats wasn’t nearly as one-sidedly Democratic as expected.
This shift of some independents who had originally intended to vote for Obama to the Republican primary to vote for McCain, explains the fact that McCain did better than predicted, and Obama did vastly worse.