His reasoning is interesting:
This time, the decision to stay out has been especially complicated by my relationship with Hillary Clinton. I am a loyalty guy, have always stuck by friends and the people who have been good to me even when I don't always agree with them, and Hillary has always been good to me personally. The Clintons brought me to Washington, took a chance on me as a very young man with little national experience. Hillary always treated me collegially and with great respect, both when I worked for her and afterwards....
However, we have now come to a crossroads in this campaign. Ironically, it was yesterday's results which have spurred my decision. If Obama had won Texas or Ohio or both, the end would be clearly in sight, and there would have been no reason for me to take the painful personal step of opposing my old friend Hillary. But I now feel it more important than ever to do so. Yesterday's victories by Hillary were impressive- as I've said before, you can never count her out. But even as impressive as those victories were, she gained very little net advantage in the delegate race. It's become increasingly clear to me that between Obama's delegate lead and the number of states left where he is likely to win big victories (WY, MS, NC, OR, MT, SD), it is virtually impossible for Hillary to gain an advantage in the pledged delegate count.
It is also clear that she won Ohio and Texas in great part to a harshly negative attack, including an ad and rhetoric on national security that completely reinforces the Bush/McCain/Republican line of attack on Democrats for the last several years.
I am not arguing that Obama is the inevitable candidate, so we should all just fall in line. In fact, I do think there is a path to the nomination for Clinton:
• She runs another harshly negative attack echoing Republican themes and beats Obama in PA
• The campaign lays heavy pressure and cuts every deal imaginable to win over a solid majority of the remaining uncommitted delegates
• The campaign then wins a bitterly negative, highly divisive credentials committee fight by a few votes
At that point, she has just enough delegates to win the nomination in a fight that goes down to convention week.
I can't think of another scenario at this point for a Clinton victory. None of the pro-Clintonites I have asked about it can spell out another way, either.
With that kind of nomination fight, the millions of African-Americans, first-time-involved-in-politics young people, and all the other Obama folks leave Denver feeling like the election has been stolen.That is not a recipe for a Democratic victory in November. As high as my regard is for Hillary Clinton, as strong as my instinct has always been to remain neutral, that kind of scenario forces me to support Obama.
However, TC thinks that the challenge is good for Obama. He needs to learn how to take a punch and it is better to learn now rather than October. TC's own guess is that this is something of a replay of the Ford Reagan race in 1976, where Ford prevailed after a late challenge from from Reagan. Ford went on to lose barely in the fall campaign to Jimmy Carter but Ford's loss was due in large part to the legacy from Watergate.