A few interesting things, just looking at the precinct map. Rubio's vote of course was heavily correlated with wealth and class. Higher income urban precincts went for Rubio in a big way, such as in Bettendorf, Iowa in Scott County. That was true all over the state. And there was one other area where Rubio can strongly, in the Dutch NW corner of the state, where Trump's vote disappeared. I guess the Dutch don't like Trump's crassness, and there Carson did particularly well. I suspect Rubio did well, because the farmers there are really wealthy. It's basically a relatively rich rural area.
The other interesting thing, is that in the southern tier of counties, Rubio's vote essentially came close to all but disappearing, and Carson did particularly well, as if those counties were the northernmost reaches of the South. They do tend to be poorer counties. In poorer rural areas, where some of the residents are not commuting to an urban area to work, Rubio did poorly. You can see that in Madison County, where Rubio did well in Winterest, particularly the wealthier part, where some folks commute to Des Moines, but very poorly in the southern part of the county, which is the poorest part of the county, with more hilly not very valuable farmland, and where folks do not commute to Des Moines.
Cruz won by doing well also with higher income voters (much better than Trump in most places), along with better than Rubio in poorer rural areas.
Rubio's performance in Calvinist Corner was striking to me as well. I had sort of assumed Cruz, who seems tailor made to appeal to a conservative Reformed audience, would improve on Santorum's 2012 performance there. But Rubio in his frequent appeals to his faith and message of American exceptionalism is a very good candidate for a significant section of the Protestant right which is tad more culturally and politically moderate than that which appeals to Cruz. (I know both types from personal experience.) From realisticidealist's excellent map, one can see that Sioux Center and Orange City rivals Rubio's best precincts in the larger urban centers. My guess is the difference between Cruz and Rubio in various precincts in the NW is more directly related to differences in educational attainment and cultural interaction than wealth.
A casual glance at the map doesn't suggest Cruz's position on ethanol hurt him in his rural support, though it might be interesting to compare the results map to the location of major ethanol refineries.
