March 09, 2007

Primary Polling Primer I: Turnout

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.

-- Mark Blumenthal

March 09, 2007 in The 2008 Race

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