That's the verdict of the polling expert this column trusts, Mark Blumenthal.

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," Redlawski 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.

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