click to enlarge
A friend of mine over at If This Be Treason laid it out like this: Hillary had nothing to gain but everything to lose in Iowa. If she didn't campaign there and Obama or Edwards won, it could be said that it wasn't a real win since Hillary didn't participate. If she participated and won, it could be said she was the presumptive front-runner and it was no big deal. But if she lost, questions would arise and power would be handed to the winner. If she lost BIG TIME, the exclamation points would add up - the questions would be more painful.
And she lost BIG TIME in Iowa. Obama has the momentum, and Edwards also, going into the New Hampshire primary. Hillary does not. You do not receive upward momentum by being a political loser.