The pace of Republican retirements predicts that Democrats should take back control of the House of Representatives this fall by a margin of eight or nine seats.
This week Edward Royce (R-CA), Chair of the House Foreign Affairs Committee, and Darrell Issa (R-CA), former Chair of House Oversight and Reform, joined 27 of their fellow House Republicans by announcing that they are retiring from the chamber. About half are leaving public office entirely, while the remainder are seeking another office like governor or senator. (Issa has threatened to run for the House again in an adjacent district.)
On the other side of the aisle, fourteen Democrats have announced that they will be leaving the House of Representatives. Only five of them are leaving public office, though Ruben Kihuen (D-NV) may be joining them subject to an investigation into allegations of sexual harassment.
Many pundits have interpreted the much higher retirement rate for Republicans to be a bellwether for this fall’s Congressional election. If no one else announces a retirement, the Republicans will face a net loss of fifteen seats going into the midterms. Just how large a threat do such retirements pose to Republican control of the House?
These two charts show the relationship between the net Republican margin of victory in terms of seats in the House and the net partisan difference in retirements. It turns out that retirements tell us essentially nothing about Congressional outcomes in Presidential years, but they are quite informative in mid-term elections like 2018. Here is the chart for Presidential years:
In presidential years we see little relationship between net Republican retirements and how well the party fares in the upcoming general election. What matters more are Presidential “coattails” with Republican swings in years when Eisenhower (1952), Nixon (1960, 1972), and Reagan (1980) ran. Democrats were favored when they ran along side Johnson in 1964, Obama in 2008, and Franklin Roosevelt in 1944.
A much different picture appears if we look at the same relationship for mid-term years.
Now the number of Republican seats won or lost depends much more directly on the number of retirements. The line is anchored by the Republicans’ success in the 1938 midterm and their dramatic losses in the 1958 election. If the figure for net retirements remains at fifteen, the Republicans are predicted to lose about thirty-two seats next November. That would give the Democrats control of the House with a margin of eight seats.
However, because the President’s party historically loses seats in midterms, we should expect to see more retirements from the President’s party in midterm years. When Democrats presided over a midterm, an average of four more Democrats retired from office than did Republicans. When the Republicans held the White House in a midterm year, retirements from their ranks outnumbered Democratic retirements by an average of six.
So some of the strong relationship we see between retirements and midterm losses arises simply because the President’s co-partisans are jumping ship knowing that their party will do more poorly in the upcoming midterm. That leaves us with the question of whether retirements have any additional predictive power once we take the President’s partisanship into account. Retirements still matter in this better specification, though that effect just achieves statistical significance.
Based on these estimates, in a year where the Democrats hold the White House, and the number of retirements on both sides of the aisle is equal, the model predicts that the Republicans should gain about thirty seats. When the Republicans hold the White House, and retirements are equal, the Democrats should gain about twelve seats (= 30.2 – 42.1 = 11.9). Regardless of which party controls the Presidency,* Republicans are predicted to lose 1.4 seats for every retirement. Applied to the current circumstances, this formula predicts a Democratic victory by thirty-three seats, or one more than predicted by the simpler model.
*Allowing the relationship between retirements and seat outcomes to vary separately depending on which party controlled the White House added no explanatory power.