He has a similar argument to Gingrich oddly enough. While he hasn't been in office for some time, he maintains credibility from earlier fame and can take some credit for the party's success (He was DNC Chairman during the 2006 and 2008 cycles.)
A former North Dakota Governor with his background could be a Republican frontrunner.
My guess is that he won't run, and that he won't do well in the primary if he does run. There's no hunger in the Democratic party for an elderly white guy. Party voters tend to prefer people who are younger, and who represent significant milestones. My guess is that someone from the Obama administration will do very well with African-American primary voters.
If Dean wins the primary, it would suggest he has more political strength than I can imagine. Perhaps he'll be a strong candidate, keeping all the Obama states except maybe Florida.
Or he might appeal to the least realistic primary voters, and go down in a landslide against a generic Republican.
