Josh makes a good point about how pundits tend to see sharp changes in momentum even though, at this point, demographic realities explain most of the primary results.

Still, I do think there was a bona fide momentum shift tonight--precisely because, as Josh says, "North Carolina was an Obama state in terms of demography and political culture ... [and] Indiana was a tossup." Given the Wright meltdown, the possibility of Obama's coalition collapsing--and North Carolina and Indiana not playing out according to form--seemed very real. That they proved resistant to Wright is a pretty important development.