Obama led the polls by a decent margin for most of the summer. McCain got a huge boost from the convention and led in nearly every poll prior the day the financial crisis broke. Then his chances sunk with it, because people blamed Bush and the GOP for what happened.
However, the financial crisis isn't why Obama got Indiana or North Carolina. In Indiana, he won because of being from Chicago and having a sort-of favorite son effect; in North Carolina it was high black turnout. And Virginia was trending D well before 2008, as demonstrated by the enormous growth of NoVa over the last few decades and that region's increasingly bluish tilt since the 90s.
I can agree with the statement about North Carolina, but Indiana was won because Obama actually campaigned there, and the rural counties swung heavily against Mccain. Traditional republicans do just as bad as Mccain did in Indianapolis these days, but can still win by almost 20 points because of the rural areas. Mccain lost lots of votes in GOP areas, and all but collapsed in the urban ones.
The democratic primary also went down to the very last few states, meaning Obama and Clinton organized the hell out of a huge number of states (IIRC, both NC and Indiana were quite competitive). The republican primary was wrapped up relatively early. This probably accounts for some of the unusual democratic strength that proved short-lived.
But also, Indiana was ground zero of the Democratic House sweep in 2006. Its flirtation with the democrats preceded Obama.
