urban:
Clinton 46%
Sanders 37%
rural:
Clinton 54%
Sanders 21%
I'd be interested in more polls that have rural/urban numbers. I remember that some of us (myself included) thought that Sanders would do well in Iowa because of the large rural population reminiscent of Vermont. Maybe it would play out in somewhere more rural like North Dakota?
Bernie is strongest in liberal areas You have a large liberal voting block in the rural areas of New England. You really don't have that in Iowa, as the more liberal areas tend to be Des Moines, Iowa City,etc and the rural sections more conservative.