Wednesday, October 06, 2010


Why the Democrats will lose the House

Back in February, I used a regression equation from Joseph Bafumi, Bob Erikson, and Chris Wlezien to show the Democrats were likely to lose the House. Although, the seasons have changed, the news remains the same. Here's why:

1. The Republicans only need to be leading by about 3% in the national popular vote to regain the House. The current aggregate of the national House ballot has Republicans teetering on the edge with a lead of about 3.5%. That lead would lead to a cliffhanger on Election Night (as Republicans need 40 seats for the majority), but it does not tell the whole story.

2. Regardless of anything else, a refined Bafumi et al. regression for the current time period for most polls (60-31 days before the Election) suggests that the party of the President is destined to better in the House vote that the September polls indicate. This makes sense as voters take into account information including the wish to bring an "ideological balance" to Washington. Voters want to check the power of the President. This wish for a check translates a Republican lead of 3.5% in September to a little greater than 5% lead in October. Now, there is an error associated with this estimate such that about 20% of the time Republicans would actually do worse than the 3.5% lead they hold currently. Still, a look at the chart below tells us that those errors happen when the non-Presidential party already holds a large House majority (1982) and the need for the aforementioned balancing is minimized; or, when the President sports a high approval rating in the mid 60's (1986 and 1998). In 2010, the party not in the White House is in the minority, and the President's approval rating is mired in the mid 40's. Thus, neither type of error seems likely to occur in this election.

3. In addition to the natural inclination towards the party out of power, Gallup finds Republicans are currently much more enthusiastic about voting than Democrats. As I noted in October, this current edge in enthusiasm is pretty much unprecedented. Why is this important? It is true that plenty of un-enthusiastic voters will cast ballots on Election Day, but a relationship between enthusiasm and likelihood to vote does exist. Since 1994, years in which Republicans held a large lead in enthusiasm (like this one) meant that they did 7-11% better among likely voters than among the larger population of registered voters. That's why the current Gallup national Congressional vote estimate of a 3% Republican lead among registered voters is actually a double digit lead (13 or 18% depending on the turnout model). The problem for Democrats is that over the past month the best have managed on Gallup's national congressional ballot is a 1% lead. Even in the best case scenario, Republicans should win the national vote by 6% and win about 228 seats in Congress.

4. What about district-by-district? The vaunted Cook Political Report finds that Democrats hold 81 seats that would be considered vulnerable, while Republicans only hold 7. An additional 5 Democratic held seats are pretty much guaranteed to go Republican. This 79 seat edge in possible seat turnover is significantly larger than in 1994 when it was only 54 seats in the final Cook ratings (which equaled the Republican seat gain). As James Campbell of the University of Buffalo found, the party who wins in a "wave election" such as 2010 is turning out to be wins at least 66% of the seats rated toss-up and even those rated leaning towards the other party. In addition, the winning party pretty much win all of the seats leaning in its direction. Considering that 73 seats lean Democratic or are tossup, Republicans should win 49 of these seats. Add that to the 10 Democratic seats that are leaning Republican or likely Republican, and Republicans could gain up to 59 seats. I should point out that Campbell's accuracy measure is from Labor Day, while I'm Cook ratings from early October. Even so, Campbell found that Republicans would gain about 51 seats using Cook's 2010 Labor Day statistics. My higher seat gain makes sense considering the Republican edge in competitive edge is now 10 seats higher than on Labor Day.

Finally, I should explain why I do not look at district polls. The fact of the matter is that they generally are not that accurate. Whether it be RT-Stategies vailient multi-district effort in 2006 or a tabulation of other publicly made available House polls from 1998-2008, house polls have a high degree of error associated with them. In effort to account for this inaccuracy (especially this far from an election), one must considerably expand the cone of uncertainty [like the forecasts at Stochastic Democracy (to which I contribute) or FiveThirtyEight]. The result is very wide confidence intervals (or large margins of error). In my mind, these intervals are far too wide in the aggregate. Yes, any one seat change has a high degree of uncertainty, but the aggregate amount of seat change is not (see points 2-4 above). Finally, both of these rely upon what is called a random walk to estimate a forecast for the generic ballot (which helps aide district-by-district estimates because of poor past polling results). FiveThirtyEight also uses a likely voter adjustment (though I believe it underestimates the eventual Republican edge) to account for point 3. The problem with these adjustments is that a random walk does not take into account point 2. We shouldn't expect a random walk, but rather a walk that aides Republicans in the national House vote.

Thus to me, it is clear that the Republicans on their way to gaining back a majority. The exact seat gain will remain uncertain until right before the election. The present Cook Political Report ratings and generic ballot suggests that Republicans will gain 50+ seats, which matches my prior February estimate. The one thing I am certain of is that something quite unusual would have to happen for Democrats to hold onto the House after November 2nd.

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