The last of the Iowa polls are in (I hope!). Today we got the final Zogby/Reuters/C-SPAN tracker, ARG and an InsiderAdvantage (based on only the top 3 candidates and with 2nd choices reallocated.) See the posts at Pollster.com for the individual poll results.
This updated "endgame" chart shows the results for both the standard and the sensitive trends. In addition, I've plotted each of the Zogby tracker results. The trend line only uses the non-overlapping tracker results so as to avoid over-counting the number of truely independent surveys in a tracker. For Zogby, this means we use 12/26-29 and 12/30-1/2 as the two trackers that are included when estimating the trend.
The Insider Advantage poll released results for all Republican candidates, but only the top three Democrats. They reallocated the 2nd choices of other Democrats. Today's release from Insider Advantage has the race Obama 34, Edwards 33, Clinton 32. On December 31, Insider Advantage released reallocated support as Edwards 41, Clinton 34 and Obama 25. That's quite a lot of change in 3 days. Since it seems unlikely actual support shifted by this much between 12/28-29 when the first poll was conducted, and 1/2 when the second was done, this is a good example of how unstable results can be when reallocating votes. We should be left with a lot of uncertainty.
The Zogby Tracking poll has moved a bit in the Republican race, and quite a bit in the Democratic. The Zogby results see a sharp move toward Obama and away from Clinton since Monday, with the final day's results moving enormously for a tracking poll. Perhaps this reflects real change, but it suggests that the final night of interviewing was somewhere between 12 and 16 points different from the sum of the other three nights in order to move the Clinton estimate by 4 points in the final poll. Obama also is credited with a 3 point move between Tuesday and Wednesday's results, likewise requiring the Wednesday nights results were far from previous ones.
Finally, ARG's recent results show a bit less net change in the Democratic race, but continue to exhibit the consistent ARG house effect we've seen before. On the Republican side, ARG does see a shift towards Romney but also a late rise for Huckabee, while McCain has moved down in their polling so his ARG results are now in line with the trend estimate.
The standard trend estimate largely ignores this cacophony, with small upward trends for Romney, McCain, Clinton and Edwards, and a slightly downward slope for Huckabee. Obama is awfully close to flat.
The more sensitive red estimator is more excited about recent developments, thinking it sees some late movement toward Obama, but not for any other candidate.
The last word on these graphs is that they also show the relative lack of late polls from a variety of polling organizations. Most polling is again from a handful of sources. This makes meaningful comparisons of house effects all but impossible, and means that our estimates of late trends are much more dependent on those few pollsters than we would wish. The stability of the blue-line standard estimator is the best comfort we have. Even with the reduction on the variety of pollsters, we aren't seeing dramatic changes in the trend estimate, implying the results are in line with pre-Christmas surveys from a larger variety of organizations.
It is 2:30 out here on the West Coast, so 4:30 in Iowa. Two and a half hours until the voters start to vote. Let's see what they think.
Cross-posted at Political Arithmetik.