Basically it happened in all the primaries where Obama couldn't game the system. Every state that had a caucus was gamed by Obama's Acorn infiltrators. That's one of the reasons the PUMA's are fighting mad.
The counterargument is that Obama did do better than expected in some primary (non-caucus) states.
But, the counter-counterargument is that Obama did better than expected in the Southern states, where a plurality of Democrats are black.