This post is part of Polyarchy , an independent blog produced by the political reform program at New America , a Washington think tank devoted to developing new ideas and new voices.

Recently, I wrote a piece asking what would happen if we accepted the increasingly overwhelming evidence that “more public participation” can’t, by itself, save American democracy. The tentative conclusion was that we needed to think harder about how “intermediary institutions” (parties, politicians, interest groups) could do a better job of helping citizens to collectively realize their interests than they would be able to do individually.

Among political scientists, the favored intermediary institution is often “political parties.” Political parties, political scientists often reason, are mass popular organizations, whose existence and success depend on mobilizing large constituencies. Because they have to appeal to a majority of the electorate to win, this should, in theory, prevent them from becoming too extreme or unresponsive. In theory, parties should converge on the mythical “median voter,” a moderate, reasonable person.

The big problem with this theory is that it doesn’t match up with the evidence. Since the late 1970s, our two major political parties have grown further and further apart by every conceivable metric. They may mobilize large constituencies. But they have been doing so in ways that are pulling to extremes, not converging on the center.

Is ideology or partisan teamsmanship the bigger problem?

In one way of thinking, the key driver of polarization is that the leaders of our political parties have not been powerful enough. Parties are too porous, and have thus been taken over by outside groups that prioritize extreme policies over everything else.

In another way of thinking, the problem is the reverse — that party leaders are actually too powerful; that they enforce too much orthodoxy on elected party members, controlling legislative agendas, and forcing members to vote in particular ways to draw contrasts with the other party so they can win elections.

In the first way of thinking, the core problem is ideology. Parties are being pulled to extreme ideological positions by powerful factions within the party.

In the second way of thinking, the core problem is teamsmanship. Factions are being pulled into zero-sum team political conflict by powerful party leaders.

If the problem is ideology, the solution is to empower party leaders to discipline these extremist groups that are pulling apart the parties, weakening the power of factions.

If the problem is teamsmanship, the solution might actually be to weaken party leaders, to let factions have more power and have space to form different types of coalitions across different types of issues, sort of like how Congress operated in the 1970s and ’80s, when party leaders were much weaker.

One challenge in ascertaining the problem is that these two approaches are often observationally equivalent. That is, when we look at polarized voting patterns, it’s hard to tell which mechanism is at work. Are parties diverging because party leaders are enforcing team orthodoxy? Or are parties diverging because factions are pulling leaders to extremes by threatening to mutiny?

One way to get more leverage on these questions would be to compare across the 50 states, since they’ve polarized to different extents.

The (weak) case that financially weak parties are to blame for polarization

If the problem is that parties are being pulled to extremes by outside groups and factions, we might expect that in states where parties can control more money, there should be less polarization. This was the contention that political scientists Raymond J. La Raja and Brian Schaffner put forth in their 2015 book, Campaign Finance and Political Polarization: When Purists Prevail. They argued that “that financially strong party organizations should reduce party polarization,” and found some evidence for it in the data, though I disagreed with them on their data analysis. I also disagreed with them on the larger thrust of their argument.

Their intuition was that competition over elections would pull parties to the median voter, who was expected to be in the political middle, thus moderating politics. "Because party insiders are chiefly interested in winning elections," they wrote, "their priority is to invest in candidates who will be most competitive in general elections — candidates whose views are closest to the median voter." (My italics.)

One implication of this intuition is that competition should move parties to the center. That is, that in more competitive states, parties should be more moderate, because parties are fighting over the median voter.

The (strong) case that strongly competitive elections are to blame for polarization

It turns out, however, that the opposite is true. The more competitive the state, the more polarized the state. This is a significant and important finding that political scientists Frances Lee and Kelly Hinchcliffe published in a 2015 article, “Party Competition and Conflict in State Legislatures,” which later became a chapter in Lee’s important 2016 book Insecure Majorities: Congress and the Perpetual Campaign. The thesis in both Lee’s book and the article is that rather than moving parties toward the middle as the median voter theory suggests, close competition actually moves parties away from the middle, because it pushes party leaders to centralize power and use that power to draw sharp contrasts.

As Lee and Hinchcliffe write, “When a political party either fears the loss of power or perceives opportunities to win power, its members have stronger incentives to step up their organizational efforts. … Close competition for party control fosters partisan contentiousness, as legislatures look for opportunities to criticize and embarrass their opponents."

The evidence in their paper is pretty compelling. So is the evidence in Insecure Majorities, as well as in Lee’s 2009 book Beyond Ideology: Politics, Principles, and Partisanship in the US Senate, which, as the title suggests, argues that something more than ideological principle has been driving polarization. That something is a struggle for power, and attempts by leaders in both parties to draw contrasts that they think set up them up better in the next election, either by making their side look good or, more often, by making the other side look bad.

There’s also evidence that partisan teamsmanship explains more than ideology among voters, too — for example, in Donald Kinder and Nathan Kalmoe’s new book Neither Liberal nor Conservative: Ideological Innocence in the American Public, which I recently reviewed in the Washington Monthly. Political scientist Lilliana Mason also has some very convincing evidence that partisan sorting, far more than ideological extremism, is to blame for the growing nastiness of polarization, since partisan sorting has increased notably over the past several decades, whereas issue positions have been mostly stable.

Tight partisan competition explains a lot more than party funding flows

Interestingly, however, neither La Raja and Schaffner nor Lee and Hinchcliffe took the alternative explanation into account in their data analysis by controlling for it in their models.

Now, along comes a new Campaign Finance Institute analysis, “Party Contribution Limits and Polarization,” which puts the two explanations for partisan polarization into the same data analysis and compares the evidence

In the head-to-head contest, there is a clear winner: Lee and Hinchcliffe’s story holds up. La Raja and Schaffner’s doesn’t. More competitive states have more polarized legislatures. By contrast, campaign finance laws had no effect. As study authors Michael Malbin and Charles Hunt write, “whether a political party was allowed to make or receive unlimited contributions had no independent effect on the level of polarization in state legislatures.”

But if close competition doesn’t produce moderate politics, then what?

The conventional wisdom is that we want close two-party competition, since elections are supposed to discipline parties into representing the median voter and reducing polarization. If competition is having the opposite effect — pushing parties further apart as they seek to draw distinctions with each other — where does that leave us?

Certainly, giving them more money will not help, since they’d just use it to run more aggressive attack ads and to discipline party members into taking more party-line votes to draw contrasts. And yet one-party democracy doesn’t seem like the answer either, since most democratic theory assumes that for there to be democracy, voters must have meaningful choices over alternatives. One-party democracy doesn’t provide that.

This is a real conundrum. As I’ve argued previously, we need better intermediary institutions, and parties are leading candidates. But under current arrangements, strengthening leaders in either of our two political parties by giving them more resources doesn’t seem like a winning strategy, given the evidence that Lee and Hinchcliffe have demonstrated.

This requires more thinking. Perhaps the answer is weaker party leaders, with more overlapping factions within parties, like we used to have. But maybe we can’t get back there. And maybe we don’t actually want to — there’s a compelling political science case that strong parties are central to democracy, because that organizes and channels conflict in ways that make it sensible and logical for voters who don’t have time to study all the issues on their own.

If so, perhaps the answer is to do away with the two-party system entirely, and move toward a multi-party system, in which case, the most essential reform right now would be to move to the multi-member districts required to make a multi-party system possible. The best way to do this would be to pass the Fair Representation Act, which was just introduced this week.

What’s clear is that two now-standard responses — strengthening our two parties and making two-party elections more competitive —are not going to reduce polarization. It’s time to move on and update our collective thinking.