For Iowa Republicans, the recruitment process is well underway as the party seeks a challenger for Sen. Tom Harkin’s seat, which he will vacate at the end of 2014.

The Democrats have tapped Rep. Bruce Braley as their likely candidate, but the Republicans have had less luck so far. Prominent Iowa Republicans, including Reps. Steve King and Tom Latham and Lt. Gov. Kim Reynolds, have all indicated that they will not run.

The search for a Republican candidate has brought attention once again to one of the most unfortunate facts of Iowa politics. Iowa is one of only four states that have never sent a woman to Congress — Vermont, New Hampshire, and Mississippi are the others.

There are, of course, some seemingly innocuous explanations for why this may be the case. Iowa’s Congressional delegation is relatively small (two senators and four representatives), and there is little turnover. Iowa Sens. Chuck Grassley and Harkin have served for 32 and 28 years, respectively.

But state-level data indicate that the gender gap in Iowa politics may not be attributable simply to these peculiarities. According to data from the National Conference of State Legislatures, Iowa ranks 27th in the nation in the proportion of women in its Legislature. Only 35 of Iowa’s 150 state legislators are women, good for 23.3 percent, just shy of the national average of 24.1 percent.

Clearly, there are factors at play in Iowa that are leading to a substantial gender imbalance in the state’s politics.

The research on this subject suggests that much of the imbalance in American politics is due to disparities in recruitment and candidate enthusiasm at every level.

According to a 2012 report from the American University Women and Politics Institute, women are significantly less likely to be asked to run for political office by political and non-political actors alike. Party officials, elected officials, and political activists are all statistically more likely to recruit men over women.

Compounding this gap in recruitment is a large enthusiasm gap. Women are less likely to be interested in running for office for a variety of reasons, according to the same report. Women are less likely to believe they are qualified to hold office, less interested in pursuing state and federal office, and more likely to hold negative views about campaigning.

These phenomena are particularly unfortunate given the many benefits of a gender-diverse legislature. Studies show that female elected officials secure more discretionary money from federal programs than men, support reproductive rights and women’s health, and increase female engagement in politics among their constituents.

Initiatives such as 50-50 in 2020, a bipartisan group that wants to increase the number of Iowa women in both national and local politics, work to decrease inequality in politics. The group’s mission is “to achieve political equity for Iowa women by recruiting, training, and mentoring women in sufficient numbers that by the 100th anniversary of women’s suffrage (2020), Iowans will have elected females to fill 50 percent of the Iowa Legislature, the Iowa delegation to the U.S. Congress and the Office of Governor.”

Given the many benefits that come from a diverse legislature, it is clear that Iowans must do more to encourage and support female candidates. Perhaps Harkin’s successor will be Iowa’s first female in Washington.

Sen. Joni Ernst, R-Red Oak may consider a run now that many of the GOPs heavy-hitters have backed out.

“This is something I have been interested in but waited for the other candidates to make their decision,” Ernst told the DI in April. “Now that Lt. Gov. Reynolds and Rep. Latham, R-Iowa, have decided they’re not running, my interest is piquing more and more.”

It’s still unclear whether Ernst will make a run at the Senate, but it is clear that Iowans must begin to cultivate a more diverse Legislature.