02/17/2007 08:17 pm ET Updated May 25, 2011

Pew Center on Past Presidential Trial Heats

The Pew
Research Center's
Nilanthi Samaranayake and Scott Keeter have posted another useful
examining the reliability of early trial heat polls in past presidential
elections. Their verdict: Not so good. While Republican front-runners have typically
won their party's nomination, "the picture is more mixed" historically for
Democrats and early general election trial-heats "have a poor track record." The
Pew analysts also point out that the past success of Republican front-runners
is of little value now since the 2008 field features "not one but two GOP
frontrunners" (John McCain and Rudy Giuliani).

Observers of the early Democratic field have been arguing
about whether Sen. Hilary Clinton's early lead in many primary trial heats
makes her nomination "inevitable." The Pew analysis provides little resolution.
On the one hand, they tell us, "early Democratic poll leaders won four out of
eight open contests between 1960 and 2004." On the other, two of the four that
did not win (Cuomo in 1991 and Hart in 1987) "withdrew from the race for
reasons other than lagging support in the polls." So make of that history what
you will.

And if that were not enough, Samaranayake and Keeter offer
another source of uncertainty for those handicapping the 2008 contests:

[T]he past polling history may be
less relevant today. The process is starting earlier than ever this year and
while there are some well known contenders, the public's level of familiarity
with the overall field of candidates is still very low. And the increased
front-loading of the primaries and the growing importance of early fundraising
means that the dynamics of the nominating process are apt to be somewhat
different this election cycle, making comparisons with past elections less

The Pew report includes a compilation of twelve early
general election trial heats ("conducted in the first quarter of the year
preceding the election" over a span of 35 years) that were "mostly wrong," either
about the winner or margin of victory. They advise that early general election
trial heats have little predictive value: "History suggests the political
climate is almost certain to change between now and November 2008."

So hold on to your hats, frontrunners, it's going to be
bumpy ride.