It's important to point out, I think, that Iowa has a bad track record of picking nominees.
In non-incumbent years, you have the eventual winner of the nomination winning Iowa 3 out of 5 times.
- : Carter wins Iowa, and wins nomination
- : Mondale wins Iowa, wins nomination
- : Gephardt wins Iowa, loses nomination
- : Harkin wins Iowa, loses nomination
- : Gore wins Iowa, wins nomination
http://www.drake.edu/public/result.html