A University of Northern Iowa political science professor has analyzed voter registration data and ranked the most-Republican and most-Democratic counties in Iowa. Christopher Larimer says his research shows why Mitt Romney’s campaign was so focused on eastern rather than western Iowa.

“There was a lot mentioned this last presidential cycle about: ‘Why on earth would Mitt Romney visit the eastern part of the state, go to Dubuque or Clinton County…or why is Paul Ryan in Black Hawk County?'” Larimer says. “Well, the answer, obviously, is vote share. I mean, they are going to get 6,000 or 7,000 votes out of Sioux County or you know, 10,000-12,000 out of those northwest counties, but that’s not going to matter much. They need to start pulling those no-party voters who are living in the eastern, more populated parts of the state.”

Larimer looked at records since the year 2000 and found the 10 most  more-Republican counties in Iowa are primarily in the western half of the state — in “very rural areas.”

“They obviously go strongly toward the Republican ticket, but they make up a very small percentage of the total number of votes going to presidential candidates,” Larimer says. “The difference with Democrats — yes, these are strong Democratic counties, but they don’t differ as much from the other 89 counties as the top 10 Republican counties did, but their vote share is much higher. You’re talking about usually 31 percent of the vote share for the Democratic candidate coming from these top 10 Democratic counties.”

Larimer also identified the counties which had the highest percentage of independent or “no-party” voters and those were in eastern Iowa.

“Eight of the top 10 no-party counties had a majority vote share, that is more than 50 percent, going for President Obama,” Larimer says. “That is very similar to the top 10 Democratic counties so, again, these no-party counties tended to be located where you have strong Democratic counties and they tend to vote like the top 10 Democratic counties.”

The counties with the highest percentage of independent voters were Floyd, Bremer, Buchanan, Delaware, Benton, Iowa Cedar and Clinton Counties. Obama won a higher percentage of the vote in each of those counties in 2012 than he did in 2008.

Larimer made his comments during a recent appearance on Iowa Public Radio.