Why is Dean slipping?

David Hogberg, live from Iowa, gives his opinion on Cornfield Commentary:

One standard explanation is the gaffe factor, that Dean’s many misstatements have made a lot of Democrats nervous. Undoubtedly, that is a big part of the reason. Here’s another: Dean is bit of a charlatan, and potential caucus-goers are getting wise to it.

I still think Dean will win Iowa, but the people that David spoke to don’t seem overly thrilled with the doctor.