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Do National Polls Inflate Clinton's Standing?


Two thoughtful but contradictory blog posts commenting on recent national presidential polling caught my eye this week. First, on Monday, "Gallup Guru" Frank Newport took issue with pundits "speculating that the race for the presidential nomination is becoming unsettled," arguing that Gallup's national data show "Hillary Clinton and Rudy Giuliani remain significantly in the lead among their respective party faithful." Then yesterday, MyDD's Chris Bowers argued that such national polls from and others assume "absurdly high" level of turnout that "inflate Clinton's perceived national advantage." Bowers sees the race between Clinton, Barack Obama and John Edwards becoming "even more competitive than we had previously surmised." Which analysis makes more sense?

First, some interests disclosed: MyDD is a popular left-leaning blog, of course, but its authors and readers tend to be more hostile to the Clinton candidacy than those who identify as Democrats on national polls. About a year ago when I was still working as a Democratic campaign pollster, I consulted with Bowers on a "Netroots" survey of members of MoveOn.org that, among other things, found that Hillary Clinton's favorable ratings were lowest among those who read blogs most often.

Moving on to the substance, I agree with the first part of Bower's argument, that national surveys typically administer their presidential primary horserace questions to a much wider slice of the electorate than will actually participate in next year's primaries and caucuses. I argued essentially the same thing in the first two installments of my "primer" on presidential primary polling.

I am not ready, however, to agree that this practice inflates Clinton's lead in national polling. What evidence I see is sketchy and contradictory. For example, Tom Riehle of RT Strategies recently shared some tabulations combining data from two recent surveys conducted by his company (in February and late March) for the Cook Political Report. Clinton wins 41% of the vote against Obama, Edwards and the other candidates on these two surveys. However, she wins more support from pure Democratic identifiers (44%) than among the independents that lean Democratic (33%). That difference is statistically significant despite the small sample sizes (n=558 Democrats, n=164 Democratic leaners). So if sampling too many voters means too many independents, it will tend to depress Clinton's vote rather than exaggerate it.

On the other hand, we did a quick comparison of national surveys fielded this year that asked the primary question of all adult Democrats (and leaners) versus those that asked the question of only registered voters that identify or lean Democratic. We looked only vote questions testing the whole field, but excluding Al Gore. Clinton received an average of 44% on four surveys conducted by Gallup and ABC/Washington Post that included all adult Democrats, and 38% on eleven surveys** that included only Democrats registered to vote (or "likely" to vote in the general election). So we have sketchy support for the notion that surveys with slightly tighter screens show Clinton with slightly less support.

Admittedly, there are many potential pitfalls with such comparisons (commenters, have at it), and none of the available data allows for a direct test of Bowers' contention. In other words, we have no survey that allows us to compare the vote among all Democratic identifiers to a theoretically "true" likely primary electorate. So I think the jury is still out.

Chris cites some data from recent LA Times/Bloomberg and Pew Research Center surveys showing Obama running much closer among well educated Democrats. And better educated adults tend to vote at higher rates than less well educated voters. That much is true, although education is just one predictor of turnout. Another is age, and the Pew survey shows Clinton with more support among older voters who also tend to turn out at higher rates.

Chris puts a lot of emphasis on recent polls in both Iowa and New Hampshire showing a much more competitive race, with John Edwards polling better and Hillary not as well as in the national surveys. That is certainly true, although keep in mind that the closer race in those states has a lot to do with John Edwards strong finish in Iowa in 2004 and his non-stop campaigning in both states ever since.

But put methodology aside for a moment: We should be looking much more closely at the early state primaries to determine how the campaigns are doing. On this last point, I tend to part company with Frank Newport. He is absolutely right that Clinton holds a formidable lead in national surveys, but the national "party faithful" will not begin to cast their ballots until after we have heard from Iowa and New Hampshire (and Nevada and South Carolina). If history is a guide, those early contests may have a big impact on the national preferences. So if we want to track the standings that matter, we should focusing on the early states.***

**The eleven surveys were conducted by CNN, NBC/Wall Street Journal, Cook/RT Strategies, Diageo/Hotline, ARG, Zogby and Democracy Corps.

***Physician, health thyself: Yes, Pollster is currently displaying charts of the national polls, but nothing on the early primaries. We hope to rectify that shortcoming very soon.

UPDATE: The just released CBS News poll confirms the pattern among independent Democrats cited above. According to the CBS pdf summary, Clinton "fares...better among Democratic identifiers than with those Independent voters who say they would vote in the Democratic primary."

 

Comments
David:

Here's another interesting set of views of the party faithful, for what it's worth: on March 6, 2007, St. Paul MN had its DFL precinct caucuses (necessary because there are local elections this year for city council and school board). The presidential straw poll produced:

25% Clinton
25% Obama
14% Edwards
9% Richardson
6% Kucinich
2% Gore (write-in)

(Although I can't find the results on the St. Paul DFL website, these are taken from a blog post and are similar to what I recall. But caveat emptor.)

Clearly, this isn't a representative sample (St. Paul is pretty left of center, but Kucinich at 6% is ludicrous), but it does suggest that hard-core party activists have not settled on a candidate.

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