Articles and Analysis


Primary Polling Primer I: Turnout

Topics: 2008 , The 2008 Race

With so many polls released in recent weeks testing the various 2008 presidential primary match-ups, now seems like a good time to take a deep breath and take a broad look at the role of public opinion polls in the race for the presidency: how they work, what they do well and what they do not so well.

Before we start considering the mechanics of how opinion polls measure voter sentiment, we really need to think about the underlying process of picking a presidential nominee and what we might like to know about "likely voter" opinion - at this stage of the process -- if we could. So before saying to much about the polls, I'd like to devote a few posts to the process.

In the United States, the two major political parties pick their nominees by a complex system of state primary elections and party caucuses that choose delegates that attend the to the national nominating conventions. While the process differs in each state, by expressing a preference for a presidential candidate, voters effectively choose convention delegates pledged to support that candidate at the convention. Many books have been written about this complex and sometimes bizarre process, but the two issues most consequential to opinion polling have to do with turnout and timing. Today I want to consider turnout and consider how much it varies from state to state.

There are many ways to calculate voter turnout, but unfortunately one of the most common - turnout as a percentage of registered voters - is difficult to do because registration procedures vary across states. To try to create more appropriate comparisons, I obtained the total number of participants in the Democratic primaries and caucuses in each state in 2004 and calculated turnout in two ways: As a percentage of all eligible adults (VEP) and as a percentage of those who would later cast ballots for Democrat John Kerry in November (details on sources below).


A few patterns are immediately obvious. First, participation in party caucuses - open meetings where participants must publicly declare their support for a candidate - typically involve just a tiny sliver of the state's Democrats. In most caucus states, participation as a percentage of those who would cast ballots for John Kerry the following November was in the low single digits. Even in Iowa - the caucus state with the highest participation rate - the estimated 124,331 Democratic participants amounted to just 17% of those who later voted for John Kerry.

Second, even in primary states, the range of turnout - as a percentage of adults, varies widely, from highs of 22.8% in New Hampshire and 21.1% in Wisconsin to the low single digits, even in blue states like New York (5.8%), Rhode Island (4.8%) and New Jersey (3.8%).

Third, the overall rate of participation is still quite low. Across all states (taking the larger turnouts from DC and Idaho which held caucuses on two different dates), Cook's figures show an estimated total of 16.8 million Democratic primary or caucus participants in 2004. That turnout amounts to a little over a quarter of the Americans (28.5%) that voted for John Kerry in November, and just 8.3% of the adults that were eligible to vote for President in 2004.

We will come back to the polling mechanics in more detail in subsequent posts, but consider the implications of the above for those national polls that ask about primary vote preference. In the context of this process, what is a "likely voter" exactly? Even if the process of identifying a likely primary voter were easy (and it isn't), the point here is that we lack a one-size-fits all definition of "likely primary voter" model that can be applied with equal precision across all 50 states.

To make all of this even more confusing, national polls typically make no effort to select likely primary voters. Most simply ask the vote preference question of adults or self-described registered voters that identify or "lean" to either the Democratic or Republican Parties. Thus, for the Democratic primary preference for example, national surveys are reporting the views of 35% to 55% of their adult samples that identify as Democrats or Democratic "leaners" when the people we really care about - those whose votes will ultimately choose the nominee - are likely to amount to less than 10% of adults.

And, for better or worse, even among that 10% some voters are going to matter considerably more than others, which brings me to timing, the subject of the next post.

Notes on the turnout table - The primary and caucus participation totals were graciously provided by the estimable Rhodes Cook (author of the America Votes and Race for the Presidency volumes published by Congressional Quarterly). To calculate percentages, I used data from the voter turnout web site maintained by GMU Professor Michael McDonald. His "voter eligible population" (VEP), a variant of the Census voting age population (VAP) statistic, is explained in more detail here.


Dwight McCabe:

I'd expect the voter particpation rate to drop off as the primary season wore on and the winner of the Presidential nomination became clear. That's pretty clearly the case in caucus states but not in primary election states.

My guess is that many state's primary elections cover many races so voting late in the primary season still has high value to voters when there are other important races open. I know you are writing about timing next and look forward to your thoughts.


Thanks for the reference, Mark. A couple of observations to your turnout analysis relevant for 2008.

Turnout is inevitably related to voter interest, which is related to the competitive nature of the election.

With one of the most wide-open presidential elections in recent history, I expect interest to be high, which should draw in some peripheral voters. Certainly turnout will be higher on the Republican side, where Bush ran unopposed in 2004. However, independent voters in closed primary states will likely be in for a rude surprise when they try to vote. If you live in New Hampshire, now is the time to change your party registration to independent so that you can take advantage of the state's primary system that allows independent voters only to change their party registration on election day.

A little-known fun fact is that New Hampshire independents who switched to the Republican Party in 2000 and wanted to vote in the Democratic primary in 2004 cast a write-in ballot. If they had coordinated on one candidate they would have just fell shy of electing a Democratic delegate to the Republican convention. My choice would have been Al Sharpton. The rule had a real effect: totalling the Republican primary write-ins for Democratic candidates along with the Democratic primary results, Clark came in second, whereas Edwards came in second among Democratic primary voters alone. Its difficult to say exactly how this affects your 2004 turnout analysis, except to say that the Kerry vote was probably slightly higher than in your table.

The other unknown in this election will be the frontloading, which should increase primary turnout in states that move up their primary since the election will still be competitive. I do not agree with the conventional wisdom that frontloading will end the election sooner, at least on the Democratic side that awards delegates proportionally to the vote (Republicans use more winner-take all rules). It is possible that because the field will still be wide open early, the delegates will be spread around enough that candidates will believe they are still viable and thus continue to hang on. It is not out of the realm of possibility that the Democrats will have a convention without a candidate with a majority of pledged delegates. This could extend the competition to the later primary states, where otherwise non-presidential primary contests would normally drive turnout.



How I got onto this page was I googled a question and perhaps you can answer this for me....are there any states that you do not have to declare your party when you vote in the primary election? I don't believe you should have to. It has no justification except to help the politicians because I know people who will not vote in the primaries because of this...so actually politicians are defeating themselves by wanting to do this.



how many states perticipate in the primary elections?


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