For 90 percent of the nation’s 435 congressional and 7,383 state legislative seats, the single most important election for politicians no longer happens in November. Far more important are the party primary elections—typically held between March and September—in which voters choose official party nominees for these and other partisan offices (like governor and U.S. senator). Win the dominant party primary, and the November contest is just a formality.

There are many reasons why so many elected offices are decided in the primaries, from gerrymandering to voters increasingly self-sorting geographically. But the problem of one-party dominance is made worse by low turnout. When fewer voters go to the polls, those who do show up are typically more motivated partisans. That, in turn, pulls both political parties to their respective extremes, especially on the Republican side.

Yet despite their importance, primary elections are largely terra incognita for electoral researchers. No national exit polls are conducted. No national foundation or academic research center regularly publishes primary turnout data, and what little research does exist focuses on presidential primary contests.

As part of our research into voting participation patterns, our team at Portland State University’s Center for Public Service set out to answer two basic questions. First, how many voters actually participate in these contests? Second, who are these voters—at least when it comes to the one data point that every state collects, their age? As is well known, older voters these days lean Republican, younger voters Democratic. Related to both questions is how states with universal vote by mail (UVBM) election systems compare to states with more traditional systems based on polling places.

To answer the first question we compiled voter registration and primary turnout statistics from all fifty states for the 2012 primary election cycle. We found that out of 190 million reported registered voters, barely 35 million cast ballots in these party primary elections. That’s a registered voter turnout of just 18 percent. By contrast, almost 70 percent of registered voters cast ballots in the 2012 presidential race, and 44 percent did so in the 2014 midterms.

Figure 1 shows 2012 primary turnout rates as we calculate them for all fifty states, based on the total number of registered voters legally eligible to participate in choosing partisan candidates on that state’s election day. In twelve states, including Oregon, only voters formally registered as Democrats or Republicans prior to election day can participate in these contests. Thirty-eight states either allow nonaffiliated voters to participate, let voters change party registration on election day, or don’t even register voters by party.

As you can see, Oregon, a universal vote by mail state, reported a 2012 eligible primary voter turnout rate of 45 percent, the nation’s highest. (That’s comparable to most states’ typical voter turnout in a regular midterm election.) The other UVBM state that year, Washington, came in at number four, with 38 percent voter turnout.

Now to the second question: What do we know about the age of the voters who cast primary ballots? For answers, we compiled data from thirteen states for the 2012 primaries and twenty states for the 2014 primaries.

Here’s what we found. For the 2012 primaries, the median age of voters was fifty-nine. By contrast, the median age of all voters in the 2012 presidential contest was forty-six, the same as the adult population overall. In other words, primary voters were thirteen years older than general election voters in 2012—a dramatic

For the 2014 midterms, the median age of primary voters was sixty-two—nine years older than the median age for 2014 midterm voters. Put another way, the typical primary voter in 2014 was sixteen years older than a typical adult—and legally eligible for Social Security benefits.

Figure 1. Turnout Among Registered Voters During 2012 Primary Election Cycle in All 50 States


That year, 2014, Colorado joined Oregon and Washington as a UVBM state. How do those three states compare to non-UVBM states? Primary voting rates for eighteen- to thirty-four-year-olds weren’t knock-your-socks-off impressive. But Oregon’s rate (13.1 percent) and Washington’s (11.2 percent) were still three to four times the performance elsewhere. Even in many states that traditionally have high voter turnout, fewer than one-twentieth of eighteen- to thirty-four-year-old voters cast a primary ballot in 2014, including Iowa (2.9 percent), Connecticut (2.8 percent), North Carolina (4.3 percent), Pennsylvania (4.8 percent), and Ohio (4.1 percent). (Colorado’s rate for that cohort was in this range, at 4.6 percent.)

So the bottom line is this. Universal vote by mail—especially in the two states, Oregon and Washington, that have had it the longest and whose voters have therefore grown most accustomed to it—yields a significantly higher percentage of voters actually casting ballots, across the age spectrum, with notable differences among eighteen- to thirty-four-year-old voters as well.

Today’s micro-turnout primaries increasingly have become electoral killing fields for candidates (including longtime incumbents) who display an insufficient ardor for a take-no-prisoners approach to lawmaking. While higher turnout in UVBM primaries certainly can’t guarantee success for less hyperpartisan and more consensus-seeking candidates, why not encourage a lot more voters to make those decisions?

Correction: The original version of this article stated that fewer than one-fifth of eighteen- to thirty-four-year-old voters cast a primary ballot in 2014 in a few high-turnout states. It should be fewer than one-twentieth.

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Phil Keisling, Stephanie Hawke, and Taylor Woods co-wrote this article. Phil Keisling, a Washington Monthly contributing editor, served as Oregon secretary of state (1991-99) and is currently the director of the Center for Public Service at Portland State University. Stephanie Hawke is a graduate student in the Public Affairs and Policy PhD program at Portland State University. Taylor Woods is a recent graduate of the Harvard Kennedy School's Master in Public Policy program and is currently a Hatfield Fellow at the Center for Evidence-based Policy.