Will Win in November?
the Generic Vote Question to Forecast the Outcome of the 2002 Midterm Election
Alan I. Abramowitz
Alben W. Barkley Professor of Political Science
Atlanta, Georgia 30322
E-mail: [email protected]
we enter the final weeks of the 2002 election campaign, most expert observers
expect little change in the makeup of the House of Representatives. In his most
recent seat-by-seat analysis, Charlie Cook of The National Journal sees
the Republicans holding a slight advantage entering the final month of the
campaign. According to Cook, 219 of
the 435 seats in the House appear to be safe for the Republicans or leaning
Republican while only 204 appear to be safe for the Democrats or leaning
Democratic. Similarly, Congressional
Quarterly’s most recent analysis of the House elections shows Republicans
favored or leading in 223 contests with Democrats favored or leading in only 203
But is it possible that these expert observers, as knowledgeable as they
are about individual House races, are missing the big picture? In some previous elections such as 1994, expert analysts have
underestimated a national trend favoring one party or the other.
Could the experts be missing a national trend favoring one party or the
other in 2002? Is it possible that
public concern about such issues as the war on terrorism or the faltering
economy could lead to significant gains for either Republicans or Democrats on
Statistical forecasting models provide an alternative approach to
seat-by-seat analyses for predicting the outcomes of House elections.
Until now, however, such forecasting models have had very limited
success. The most accurate such
model, one developed by Gary Jacobson of the University of California at San
Diego, utilizes the incumbent president’s approval rating, the change in real
per capita income in the year preceding the election, and a measure of seat
exposure (the number of seats held by the president’s party compared with its
normal strength), along with an adjustment to incorporate an increase in
Republican strength since 1990, to predict seat gains or losses by the
president’s party. However,
despite its complexity, this model only explains about 70 percent of the
variance in the outcomes of House elections since World War II.
This paper proposes and tests a new and relatively simple forecasting
model for midterm House elections based on the results of the Gallup Poll
“generic vote” question. Prior
to every midterm election since 1950 with the exception of 1986, the Gallup Poll
has asked a national sample of likely voters which party they plan to vote for
in the election to the House of Representatives from their district.
Even though the generic vote question does not provide respondents with
the names of the Democratic and Republican candidates in their own district, it
is a fairly accurate predictor of the number of seats won by the parties in
midterm elections. By regressing
the number of seats won by the Democrats in midterm elections on the Democratic
lead or deficit in the generic vote, we obtain the following result (with the
estimated standard error shown in parentheses):
Dem Seats = 3.67(.550)*Generic + 226.1.
The generic vote variable by itself
explains about 80 percent of the variance in the outcomes of midterm elections
since 1950. The standard error for
this single variable model is only 12.3 seats—much smaller than that of any
previous forecasting model.
estimated coefficient of 3.67 for the generic vote variable means that every one
percentage-point increase in the generic Democratic vote is worth an additional
3.67 Democratic seats in the House of Representatives.
While these results are impressive, we can improve the accuracy of the
generic vote model by adding two additional predictors: the number of House
seats held by the Democratic Party before the midterm election and the
president’s party affiliation. The
number of House seats held by Democrats before the election measures the
advantage of incumbency—the more seats with a Democratic incumbent, the more
seats the Democrats should win. The
president’s party affiliation, a dummy variable taking on the value 1 if there
is a Democratic president and 0 if there is a Republican president, should
capture the impact of negative voting: in midterm elections, discontented voters
are more likely to vote against the president’s party than contented voters
are to vote for the president’s party.
Regressing the number of seats won by the Democrats in midterm elections
on the Democratic lead or deficit in the generic vote, the number of Democratic
seats in the previous House, and a dummy variable for the party of the
president, we obtain the following results (with the estimated standard error
for each predictor shown in parentheses):
Dem Seats = 3.00(.278)*Generic + .453(.070)*Previous Seats –
19.9(4.06)*Democratic President + 127.3.
Despite the small number of elections
available for analysis, all of the estimated coefficients are highly
statistically significant. The model now explains an impressive 96 percent of the
variance in the outcomes of midterm elections since 1950 and the standard error
of the model is only 5.4 seats. According
to these results, every one percentage point increase in the generic Democratic
vote is worth an additional three Democratic seats in the House of
Representatives, every seat held by Democrats before the election is worth an
additional .45 Democratic seats after the election, and the presence of a
Democrat in the White House costs Democrats an average of just under 20 seats in
a midterm election.
Based on these results, what should we expect in the 2002 midterm
election? The following table
displays the number of House seats that the model predicts will be won by
Democratic candidates based on the Democratic lead or deficit in the generic
vote in the final Gallup Poll before the election.
In Generic Vote
Predictions shown in boldface indicate Democratic majority
The results of the most recent Gallup Poll, based on interviews conducted
from October 3-6, show Democrats leading Republicans in the generic vote by 48
percent to 47 percent, with five percent undecided.
Based on this one point lead, the three-variable generic vote model
predicts that Democrats will win 226 seats in the 2002 midterm election while
Republicans will win 209 seats. This
would be a pickup of 14 seats for the Democrats.
Even if the Democrats are even with Republicans or trailing by one point
in the generic vote, the model predicts that they will regain control of the
House, although by a very narrow margin. Thus,
in contrast to the expert observers, the generic vote forecasting model gives
Democrats an excellent chance of regaining control of the House of
Representatives on November 5th.