I'm gonna guess that there's great grass roots involvement at the caucus level than in primaries, and those races tended to go more towards the candidates favored by the more ideological/anti-establishment end of the party.
Okay, I understand why Obama could mobilize his grassroot supporters.
But why didn't McCain have any? I thought there were millions of supporters who had been eager for decades to vote for him.
Maybe, but not in the conservative Interior West, especially against the support 2008 Romney was apparently getting.
