Generic House Polling Suggests the Republicans Could Regain the House in 2010

Under the heading, “Republicans not in a position to retake the House (yet),” Chris Bowers estimates that the Democrats have a 41.2%-37.7% lead in recent generic House polling. Bowers writes, “Democrats are, after all, still winning.”

But it’s not so simple. In research published a couple years ago, Joe Bafumi, Bob Erikson, and Chris Wlezien found that, yes, generic party ballots are highly predictive of House voting–especially in the month or two before the election-but that early polling can be improved by adjusting for political conditions. In particular, the out-party consistently outperforms the generic polls.

(click to enlarge)

The paper accompanying this graph was among the first public predictions of a Democratic takeover in 2006.

Bafumi, Erikson, and Wlezien’s analysis doesn’t go back before 300 days before the election, but if we take the liberty of extrapolating . . . The current state of the generic polls gives the Democrats .412/(.412+.377) = 52% of the two-party vote. Going to the graph, we see, first, that 52% for the Democrats is near historic lows (comparable to 1946, 1994, and 1998) and that the expected Democratic vote–given that their party holds the White House–is around -3%, or a 53-47 popular vote win for the Republicans.

Would 53% of the popular vote be enough for the Republicans to win a House majority? A quick look, based on my analysis with John Kastellec and Jamie Chandler of seats and votes in Congress, suggests yes.

It’s still early–and there’s a lot of scatter in those scatterplots–but if the generic polls remain this close, the Republican Party looks to be in good shape in the 2010.

P.S. Is there any hope for the Democrats? Sure. Beyond the general uncertainty in prediction, there is the general unpopularity of Republicans; also, it will be year 2 of the presidential term, not year 6 which is historically the really bad year for the incumbent party. Still and all, the numbers now definitely do not look good for the Democrats.

About Andrew Gelman 26 Articles

Affiliation: Columbia University

Andrew Gelman is a professor of statistics and political science and director of the Applied Statistics Center at Columbia University. He has received the Outstanding Statistical Application award from the American Statistical Association, the award for best article published in the American Political Science Review, and the Council of Presidents of Statistical Societies award for outstanding contributions by a person under the age of 40.

His books include Bayesian Data Analysis (with John Carlin, Hal Stern, and Don Rubin), Teaching Statistics: A Bag of Tricks (with Deb Nolan), Data Analysis Using Regression and Multilevel/Hierarchical Models (with Jennifer Hill), and, most recently, Red State, Blue State, Rich State, Poor State: Why Americans Vote the Way They Do (with David Park, Boris Shor, Joe Bafumi, and Jeronimo Cortina).

Andrew has done research on a wide range of topics, including: why it is rational to vote; why campaign polls are so variable when elections are so predictable; why redistricting is good for democracy; reversals of death sentences; police stops in New York City, the statistical challenges of estimating small effects; the probability that your vote will be decisive; seats and votes in Congress; social network structure; arsenic in Bangladesh; radon in your basement; toxicology; medical imaging; and methods in surveys, experimental design, statistical inference, computation, and graphics.

Visit: Andrew Gelman's Website

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