Volume 25: Back to the House
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A bigger and better log-loss comparative analysis of quantitative and qualitative projections for the 2020 U.S. House of Representatives elections
We’re back at it.
After 2018’s well-received analysis of the accuracy of House race raters and modelers, we’ll make another attempt for 2020. But we’re including more participants, gathering more data, and producing more analysis.
Especially in years with Presidential elections, Congress tends to get the short end of national attention. This is especially true for the House of Representatives, and it is unfortunate. Although its members are often little known and its behavior is occasionally unruly, the House is the closest body we have to a representative and responsive federal democracy. It is not separated from the voters by an electoral college. It does not have widely disparate representation depending on which side of a state line you live. It is not appointed and confirmed—it’s elected directly, by all of us.
It is, also, fascinating for a statistician. Presidential and Senate races are plagued by small sample sizes. A set of 435 samples is much more fun. So, it’s in the House where we’ve been gathering data, and in the House where we will carefully consider the results.
What's this project again?
In addition, I have created my own qualitative ratings for each district.
The significant difference from our previous analysis is that we do not have only the current ratings for each seat. We have, in fact, been capturing all ratings changes since each forecaster’s launch. This collection of data will allow for an analysis of how the national environment has changed over the election cycle—at least, as it is represented by these forecasters’ predictions. This also allows us to run other interesting analyses, for example, a time series of the accuracy of each forecaster by day. Hopefully, we’ll see them getting more accurate as the election gets closer, demonstrating that the professionals are understanding and incorporating news and data as it becomes available.
What are the experts saying?
We’ve undertaken this project despite the fact that control of the House of Representatives after the upcoming election is not really in doubt.
Recall that in the 2018 election, the House was retaken by the Democrats, gaining 40 seats and winning the overall House vote by about 8% nationally. Democrats won seats that had been traditionally Republican, or had been won by Donald Trump in 2016, or both. Because of this, at the start of the current election cycle, most expected a rebound in GOP fortunes. The question being asked was whether Nancy Pelosi would be able to hold on to a slim majority. Now, the quantitative and qualitative experts unanimously agree that the Democrats are more likely than not to gain seats on November 3rd, building on their gains from the 2018 elections.
There are several reasons that views about this cycle have changed. First, court-ordered redistricting in North Carolina has likely moved two seats to the Democrats, right off the bat. Second, several popular GOP incumbents in swing seats are not running (for example, TX-23, GA-07, and IN-05). Third, several GOP incumbents have lost primaries that unnecessarily put seats in play (CO-03 and VA-05). Then, the GOP had recruitment failures in several districts ripe to be retaken (ME-02, NY-19, and KS-03, among others). Finally, the unpopularity of Donald Trump has put more traditional Republican seats in play (IL-13, NY-02, and MO-02). Also, several freshman Democrats are running noticeably effective campaigns in otherwise tough seats (SC-01, CA-45, and UT-04).
The Republicans do have a few bright spots. David Valadao, a popular incumbent who lost a close race in CA-21 in 2018, returned for a rematch. Freshman Debbie Mucarsel-Powell drew a strong opponent, Carlos Gimenez, the popular, long-term GOP mayor of Miami-Dade County. Dave Loesback, a Democrat from the swingy IA-02, hung up his spikes after seven terms.
But on net, the Democrats are viewed to hold the stronger hand, irrespective of their large existing majority. We see this by looking at each rater’s expected number of Democratic seats. Recall that the Democrats currently hold 233 seats to the Republicans’ 202.
As you can see, all the raters in our project now expect the Democrats to gain seats. The spread between the forecasters is small; only seven seats from low to high estimate. This is a high level of agreement and causes me to wonder if there is some amount of herding going on.
Looking at ratings as a time series, we can see that the forecasters’ views have been moving steadily toward an expanded Democratic majority throughout the summer and fall: