Iowans are nice, they reward nice candidates and they don't like confrontation.
Chuck Todd's take on this morning's Democratic debate is basically equivalent to mine, so, in an effort to save some paper:
Overall, this is a debate that had "August" written all over it, meaning the candidates decided not to take advantage of opportunities to engage. Instead, at almost every opportunity, the frontrunners took pains to NOT engage even when questions from the moderator tried to create spats. So in the absence of a "moment," it's hard not to declare Clinton the winner of this debate because, like boxing, if the champ doesn't get knocked out, then the champ is still the champ.
This is not to say Obama and Edwards did poorly in this debate. To the contrary, both seemed more presidential than in previous debates but neither seemed comfortable trying to take down the frontrunner. Edwards and Obama took veiled shots at Clinton but in a way that was, well, "Iowa nice."
One glaring missed opportunity for Obama to show contrast with Clinton came, not from a moderator question, but from a voter question who asked about a time when the candidate didn't say everything they thought. Remember, Clinton critiqued Obama for saying everything he thought. If the places were reversed, Clinton would not have missed an opportunity like that. This is where Obama's inexperience as a politician shows. He's just not very tactical, which to some may seem like a refreshing change but in primary politics, isn't a recipe for success. Frankly, it was a moment of political campaign inexperience. Tactically, these debates do show that Obama hasn't had many tough campaigns, which may explain why he misses opportunities like this one.
The MSNBC Iowa focus groupers seemed to disagree, BTW.