One of the biggest boosts Edwards got in IA seems to be how many votes he picked up from supporters of non-viable candidates. In a primary you don't get a trial run to determine if your candidate is viable so you have to decide ahead of time whether your candidate is viable and whether or not that really matters to you.
Based on current polls the "major" candidates who are supported by less than 15% in NH are Edwards and Lieberman. This could change prior to the primary date -- I suspect Edwards will pass it and Dean could fall apart in some kind of visious circle of people losing faith in him because others have and so on. It would be nice for a candidate if he could pick up the Lieberman vote before these people actually vote. It seems like Edwards might be heading in that direction (contiously or not). He is already the most pro-Iraq war candidate after Lieberman and now he is beginging to play up
morality (another aspect Lieberman or Lieberman's campaign).