Mark Blumenthal | August 9, 2007
Topics: 2008 , Iowa , Likely Voters , The 2008 Race
A few additional notes on the poll of
likely Iowa caucus-goers from the University of Iowa
that we linked
to earlier, based on information provided via email by U. of Iowa Assoc. Prof. David
First, the survey used a sample drawn from a list of Iowa households listed in telephone directories. As such, it has a potential coverage problem because it misses Iowans with unlisted telephone numbers. The survey screened to interview 907 self-reported registered voters.
Second, "because of a programming glitch," Redlawsk said he "cannot distinguish the 'no registered voters' from other refusals." However, we know that as of the fall of 2006, 84% of Iowa's adults were registered voters (1.9 million** registered voters divided by 2.26 million voting age adults).
Based on that statistic, we can make the following assumptions about the percentage of adults represented by the various subgroups reported on for this survey:
- 425 Democratic Caucus Goers = 40% of adults
- 319 "Most Likely" Democratic Caucus Goers = 29% of adults
- 306 Republican Caucus Goers = 28% of adults
- 223 "Most Likely Republican Caucus Goers = 21% of adults
In short, the various subgroups of likely caucus goers in the U. of Iowa poll represent a much broader slice of Iowa voters than the recent ABC/Washington Post survey or the Des Moines Register survey from last year.
Put another way, even the "most likely" caucus-goer
definitions for this survey project to a combined Democratic and Republican
turnout of 1.1 million participants -
half the adults in Iowa.
By comparison, Democratic turnout was an estimated 124,000
147,000 in 2004, and estimated Republican turnout
was 108,000 90,000 in 1988.
Finally, even putting screening issues aside, this survey used an entirely open-ended vote preference question. Respondents had to volunteer the name of their choice without prompting. This method undoubtedly provides a tougher test of voter commitment, but also produces a much bigger undecided and renders the results incomparable to other Iowa polls. As such, we have not included either of the U. of Iowa polls in our Iowa charts.
**UPDATE: In doing these calculations, I should have added a decimal to the registered voter number (i.e. 1.97 voters rather than 1.9) which would have shown 87% as registered to vote rather than 84%. That change would increase my estimate of the percentage of adults represented by each sample to 30.6% for the "mostly likely" Democratic caucus goers and 21.4% for the "most likely" Republicans.