More on Party ID

Legacy blog posts Weighting by Party

My post on weighting by Party generated by far the most comment, and has left a few good questions unanswered. I’ll try to answer them in the next several posts.

For now, let me add some additional data released by the Pew Research Center last week that I had missed (thanks for the tip to in-the-know emailer Mr. X). Their report covers a lot of the same ground as I did, but adds some very pertinent data. Here are the highlights, but read it in full:

They include the most complete summary I’ve seen yet on changes in Party ID before and after the Republican convention as reported by Pew, ABC/Washington Post, CBS NYTimes, Gallup/CNN/USAToday and Newsweek among registered voters (including data not included in the public releases). Each survey shows relatively small increase in Republican identifiers (+1 to +5) and similarly small shifts away from the Democrats (-2 to -6). If you average the results for the five organizations, we see a five-point Democratic advantage in early August (37%-32%) shift to a two point deficit in September (33%-35%).

Pew also reports data from three “panel” studies – from 1988, 1992 and 2000 — that interviewed respondents from the same random sample twice: once several weeks or months before the general election and again a few weeks after.
· In 2000, 18% of respondents changed their answer between September and November
· In 1992, 26% changed their party identification between June and November
· In 1988, 16% of the sample changed its party identification in just two weeks, shifting from a 5% Democratic edge (35% to 30%) to an even division (33% to 33%). Note the similarity in both time and magnitude to the shifts seen this month.

Finally, Pew includes a graphic showing trends in Republican identification as measured by Gallup over the last two years, that shows frequent spikes and drops drops that often follow major events, including a roughly 10-point GOP gain around the capture of Saddam Hussein.

All of which suggests that the slight increase in Republican party ID evidenced on polls last month is entirely plausible, but may also be quite short lived. Pollsters weight by long term averages in Party ID at their own risk.

Bonus: Gallup’s Frank Newport’s blog covers much of the same ground (hat tip to Dalythoughts). Thanks to Newport for the link.

[Continue with Why & How Pollsters Weight, Part I]

Corrected Name of Pew Research Center (10/29)

Mark Blumenthal

Mark Blumenthal is political pollster with deep and varied experience across survey research, campaigns, and media. The original "Mystery Pollster" and co-creator of Pollster.com, he explains complex concepts to a multitude of audiences and how data informs politics and decision-making. A researcher and consultant who crafts effective questions and identifies innovative solutions to deliver results. An award winning political journalist who brings insights and crafts compelling narratives from chaotic data.