The disappearance of competitive congressional elections is one of the starkest political trends of the last half century. According to an analysis by the Cook Political Report, during the last 20 years alone, the number of competitive House districts has declined by more than 50 percent. In the 2016 election, just 17 percent of districts were competitive.

Gerrymandering often takes the blame for that decline and the partisan polarization that has followed. As President Obama said during a 2015 interview with NPR:

I think political gerrymandering has resulted in a situation in which — with 80 percent Democratic districts or 80 percent Republican districts and no competition, that that leads to more and more polarization in Congress, and it gets harder and harder to get things done.

But the relationship between gerrymandering and the decline in competitive elections is not as straightforward as Obama makes it sound.

This is the fourth installment of FiveThirtyEight’s podcast series “The Gerrymandering Project,” in which we travel around the country to explore the effects of gerrymandering and what reformers are doing to change the redistricting process. In this episode we look at an effort to foster competitive elections in Arizona.

In 2000, Arizonans voted to take the responsibility for drawing political maps away from the state Legislature and instead give it to a bipartisan commission of citizens. One of the criteria for drawing maps in the new law was the “creation of competitive districts where there is no significant detriment to other goals.”

A fiercely partisan debate over the meaning of that guideline broke out during the 2011 round of redistricting. At what point does creating competitive districts become a “significant detriment” to keeping cities, counties or communities of interest together? Republicans who had supermajorities in the state Legislature at the time were not in favor of more competition and instead stressed communities of interest, which are not defined in the Arizona law but were based on geography and other commonalities among citizens. Democrats, who wanted a shot at winning more seats, were all for increased competition.

The independent chair of the five person commission, Colleen Mathis, was the tiebreaker between the two Republicans and two Democrats. It became an ugly standoff with threats to Mathis’s safety.

Beyond the partisan positioning is an important question about why competitive elections have disappeared and what we can do to foster them. Gerrymandering is probably not the main culprit in their disappearance. But redistricting isn’t completely off the hook either. So what role can redistricting play in fostering competitive elections, and is it worth the partisan battles?

To hear the story, click on the play button above or subscribe to The Gerrymandering Project podcast feed. And while you wait for the next episode, be sure to join our Gerrymandering Project Facebook group. It’s a place to share your experiences with and opinions about gerrymandering. We’ll be having conversations there every week.