Do National Polls Inflate Clinton's Standing?

04/13/2007 04:09 pm ET | Updated May 25, 2011

Two thoughtful but contradictory blog posts commenting on
recent national presidential polling caught my eye this week. First, on Monday,
"Gallup Guru" Frank
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"
of members of that, among other things, found that
Hillary Clinton's favorable ratings were lowest among those who read blogs most

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

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
and Pew Research
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."