The Iowa caucuses are of course different than other primaries and elections. Democratic ballots are not secret. However, the time costs are greater. A lot of research on voter participation mentions the importance of social pressure and how election design should affect voter behaviour.

Is there any existing research that compares and contrasts voting behaviour (turnout, trends based on the closeness of the race, etc) in Iowa vs. in other elections?

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    Iowa only uses caucuses for their 'primaries' -- the final elections are the same as any other in the US. Also, many other states use caucuses instead of secret ballots for 'primaries'. To the best of my knowledge, the key difference with the Iowa caucuses is the fact that they're first, no that there's anything unique about them.
    – divibisan
    Mar 21, 2018 at 21:05

3 Answers 3



There is very little difference between primary and caucus voters, and also very little difference between caucus/general election voters as well. Primary/caucus voters tend to be older and a little more ideological (see quote below), and the size of the differences is almost exactly the same between caucus and primary voters.

There is an excellent paper that summarizes some of the behaviors you question, entitled Demographics of Primary, Caucus, and General Election Voters. The abstract is:

The objective of this research project is to analyze the demographic characteristics of voters in Iowa, New Hampshire, and Ohio in order to determine if there are significant differences between primary, caucus, and general electorates and to investigate the consequences of these differences for election outcomes.

And contains interesting nuggets like:

Nownes offers further support for this idea in his article “Primaries, General Elections, and Voter Turnout: A Multinomial Logit Model of the Decision to Vote.” Using data from the 1988 National Election Study, Nownes modeled the dynamics that led voters to vote on both the primary and the general election, only in the general election, or in neither the primary nor the general. He finds that “[there] is no evidence […] that primary voters are more efficacious, ‘dutiful,’ concerned about the election outcome, or informed, than other voters. In short, individuals who vote in both [primary and general] elections are not much different than individuals who vote only in the general election. Both sets of voters share many of the same characteristics” (Nownes 1992, 219). These findings call into question other studies concluding that primary voters are vastly ideologically and demographically distinct from the general electorate.


I offer this only as a partial answer. One defining characteristic of the Iowa caucus in recent decades is the overwhelming relevance of the ethanol issue. Iowa's economy is largely based around corn, and corn can be used to make ethanol as a fuel additive for gasoline. Therefore, federal subsidies for ethanol production are an issue that significantly rewards the state economy of Iowa. This also means that candidates taking the "ethanol pledge," meaning that they show support for ethanol subsidies, are rewarded by the Iowa caucus.


The media seems to emphasize Iowa caucuses primarily because they are first. For this reason they may tend to weed out candidates with weak support because funding for weaker candidates dries up. The general idea seems well supported by the 2016 GOP caucuses results, but the eventual winner placed only 2nd in a close race between 3 top contenders. In the Democratic party caucuses, the top two candidates (Clinton & Sanders) were in a near tie.

But caucuses and primaries are not necessarily an either-or matter. Washington State for example seems to have both. But results there seem so confused it becomes hard to say there's a pattern:

Washington State voters in 2004 supported implementation of a "top-two" primary system, but the state's Republican, Democratic and Libertarian parties all didn't like it, and sued claiming it violated the parties right to free association. In 2008 the U.S. Supreme Court overturned a lower court ruling, and later that year Washington state had the first "top two" primary election in the country.

In 2012 there was further controversy, despite having been described by press sources as "low-key":

In the Washington State 2016 Democratic caucuses, Bernie Sanders received almost 73% of the votes, however Clinton won the primary by 52%.

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