Midterm history gives Republicans a fighting chance in November

It is nearly axiomatic that every sitting president’s party loses seats in midterm elections. It is how America’s political tides run. Presidential elections swell voter turnout, and the winning candidate’s party benefits. Midterms see the voter turnout tide recede, and the ebb costs the president’s party votes and seats in Congress.

My calculations of official House and Senate records from 1926 through 2022 found that the president’s party has lost an average of 11.3 percent of its House seats and 6.7 percent of its Senate seats in midterm elections. Based on this overall average, Republicans would lose 25 House seats and four Senate seats in November. 

However, buried within this century-long trend is a lot of variability.

For one, average congressional losses have been much lower since 1986. I found that in midterms from 1986 to 2022, the president’s party lost just 9.2 percent of its House seats and 5.8 percent of its Senate seats. One reason for the disparity is likely the parties’ increased ability to gerrymander House districts to their benefit, reducing toss-up seats. Another is the sample period itself: 1986-2022 excludes the volatile Great Depression and immediate postwar years.

Based on the 1986-2022 trend, Republicans would lose 20 House seats and three Senate seats in November — the latter being particularly significant because it would result in a 50-50 tie, with Republicans retaining Senate control with Vice President JD Vance’s tie-breaking vote.

Another important variable is that not all midterms are the same. From 1986 to 2022, during second midterms, the president’s party performed better in the House, losing only 5 percent of seats, but worse in the Senate, losing 10.7........

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