October 29, 2007

Details on the New University of Iowa Poll

As promised, we have a new Iowa poll today. But be sure you read the fine print below.

Let's start with the basic "poll update" that the estimable Eric Dienstfrey usually posts in this space. A new University of Iowa "Hawkeye" poll of 689 likely caucus goers in Iowa (conducted 10/17 through 10/24; summary, methodology, presentation) finds:

• In an open-ended question where 306 Democrats had to volunteer, without prompting, the name the candidate they are supporting, Sen. Hillary Clinton (at 29%) edges out Sen. Barack Obama (at 27%) in a statewide caucus; Sen. John Edwards runs at 20%, Gov. Bill Richardson at 7%, Sen. Joe Biden at 5%. All other candidates receive less than five percent each.

• In an open-ended question where 282 Republicans had to volunteer the name of the candidate they are supporting, former Gov. Mitt Romney leads former Mayor Rudy Giuliani (36.2% to 13.1%) in a statewide caucus; former Gov. Mike Huckabee trails at 12.8%, former Sen. Fred Thompson at 11%, former Sen. John McCain at 6%. All other candidates receive less than five percent each.

Readers should consider that the methodology of this survey, as in August, is different from most of the other Iowa caucus surveys we have seen. According to Professor David Redlawski, who spoke at a Washington press briefing this morning, the October Hawkeye this most recent survey used essentially the same methodology as their August survey. That is, it used an open-ended vote question, the same screening questions and sampled from a list of telephone numbers drawn from listed telephone directories (i.e. not a registered voter list and not using a random digit dial methodology).

The summary posted by the Hawkeye pollsters includes information on their screening procedure. They report that the two "likely caucus goer" samples represented 55.8% of their "registered voter contacts" (that is, of adults who said they were registered to vote), that 58.6% of these said they would attend the Democratic caucus and 41.4% would attend the Republican* caucus.

If we assume that 87% of Iowa adults are registered to vote (1,970,110 "active" registered voters divided by 2,264,010 Iowa adults), that means that the Democratic sample represents 28% of Iowa adults and the Republican sample represents 20% of Iowa adults. [Correction: The screening information initially provided by the University of Iowa and quoted above was in error and skewed these calculations. The correct percentages of Iowa adults represented were 17% for the Democrats and 13% for the Republicans. See the update at the end of this post for more details].

The problem with that is that it projects to a "likely caucus goer" universe of nearly half the adults in Iowa - more than a million. The estimated Democratic turnout in 2004 was 124,000 - the previous all-time high was 126,000 in 1988. The all-time high for Republicans was 106,000, also in 1988. So this poll is sampling a considerably broader population of Iowa adults than has turned out to attend past caucuses.

So interpret these results in that context and with great caution. The trends observed by comparing the August an October Hawkeye polls are meaningful - because they used the same methodology for both polls - but apply only to the very broad population of Iowa adults sampled. It helps that the trends in this poll bear a resemblance to what we have seen lately on other Iowa polls, but we advise huge grains of salt before comparing the support for any particular candidate on this survey to that measured by any other survey.

*Typo corrected. Thanks James.

Update - 12/16/2007: The original PDF release put out by the University of Iowa that I used in making the above calculations included the following sentences:

Respondents were asked whether they were very likely, somewhat likely, not very likely, or not at all likely to attend their party’s caucus in 2008. Responses of “not at all likely” were screened out of the sample. Remaining respondents were further asked which party's caucus they would attend. Those unable to name which party were also screened out of the sample. Of registered voter contacts, 36.2 percent were eliminated on the initial screen. Another 8.0 percent were screened out because they could not name the party with whom they would caucus.

On December 13, 2007, The University of Iowa's Caroline Tolbert notified me via email that the paragraph above was incorrect. They subsequently revised the paragraph in their summary to read as follows:

Respondents were asked whether they were very likely, somewhat likely, not very likely, or not at all likely to attend their party’s caucus in 2008. Among all registered voters contacted, 37.2% said they were "not at all" likely to caucus, while another 21.3% said they were "Not very likely". These two groups were not considered "likely caucus goers". The remaining 41.5% said they were "Very Likely" (24.1%) or "Somewhat Likely" (17.4%) to caucus. A second screen then asked which party's caucus the voter planned to attend. Of the initial screen of likely caucus goers, 4.4% could not name a party, and were dropped. Approximately 35% of the original registered voter sample is thus classified as "likely caucus goers". Of the total original registered voter sample, about 19.1% are likely Democratic caucus goers and 14.4% are likely Republican Caucus Goers.

Since my calculations were based on the erroneous information included in the first release, they too were in error. The correct statistics, based on this new information, are as follows: The Democratic sample represented 17% of Iowa adults, the Republican sample represented 13% of Iowa adults.

-- Mark Blumenthal

October 29, 2007 in Disclosure, Iowa

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