聽說這次玉米粥會激戰？
顏色對照表如下(數字為該黨得票率)：
https://i.imgur.com/xeKnn31.png
這裡值得注意的地方如下
https://i.imgur.com/zhX08EW.png
圖案如下：
1990:
Tom Harkin Democratic 529571 53.82%
Tom Tauke Republican 453273 46.07%
https://i.imgur.com/LXgB0vn.png
https://i.imgur.com/RBWF2gT.png
1996:
Tom Harkin Democratic 634166 51.81%
Jim Ross Lightfoot Republican 571807 46.71%
https://i.imgur.com/HsvCT3c.png
https://i.imgur.com/KQmqBpH.png
2002:
Tom Harkin Democratic 554278 54.18%
Greg Ganske Republican 447892 43.78%
https://i.imgur.com/OADCkux.png
https://i.imgur.com/WWJcdPS.png
2008:
Tom Harkin Democratic 941665 62.66%
Christopher Reed Republican 560006 37.26%
https://i.imgur.com/x92njG0.png
https://i.imgur.com/otfV2Lc.png
2014:
Joni Ernst Republican 588575 52.10%
Bruce Braley Democratic 494370 43.76%
Rick Stewart Independent 26815 2.37%
https://i.imgur.com/zS3F4VZ.png
https://i.imgur.com/gEk6Shd.png
選舉資料來源：
Leip, David. Dave Leip's Atlas of U.S. Presidential Elections.
http://uselectionatlas.org (date).