Had So Many Not Retired……

The Republican Party found itself in an unfamiliar position on November 7, 2018. For the first time since 2010, the Democrats had gained control of the house, flipping 40 seats. This was not entirely unexpected. With 41 Republican seats vacated due to retirement or incumbent members running for senate, the house seemed like a lost cause from the start. Unlike in other midterm waves however, House success did not translate into senate success, as the Republican expanded their majority by two seats. So did the record number of vacancies cost the Republicans the House?

To answer this question, it is important to identify where the vacancies were located. Of the 41 vacancies, roughly 11 were in safe red states, such as North Dakota, Idaho, Texas etc. These seats did not require the advantage an incumbent brings to the table, as many were won by 20 or more points by the GOP. With this in mind, there are still 31 seats left to analyze, more than enough for the Democrats to take control of the house.

Since we have ruled out the races where in the incumbent advantage was not a factor, it makes sense to swing to the other direction. In South Carolina’s 1st district and New Mexico’s 2nd district, fresh Republican candidates lost by less than one percent. Now, the extent of the incumbent advantage is often debated, but you would be hard pressed to find anyone who would argue having an incumbent would not have swung these districts. Similar instances occurred in CA-03, FL-27, and WA-08, where Democrats flipped the seats by 6 or less. These races provide proof that vacant seats are vulnerable seats.

The remaining races took place in traditional swing districts that typically decide control of the house. Florida, New Jersey and Pennsylvania are particularly relevant, as 8 vacant Republican seats were contested in these House Swing states. Republicans managed to go 4-4 in these particular races.  Factoring in the large losses in AZ-09 and CA-49 that were likely inevitable with or without an incumbent, Republicans went a respectable 30-11 defending vacated seats. It is rather difficult to pinpoint the exact reason swing districts flip, as they are often won narrowly under any circumstance, lacking incumbents in these crucial districts most likely contributed to these losses.

If we assume the incumbent advantage is worth roughly 3-5 percentage points in an average house election, Republicans would have retained 4-5 of those 11 lost seats. Given that the Democrats flipped 41 seats to obtain a 36 seat margin of control, vacated seats are not the reason the GOP lost control of the chamber. Even if the party retained all 41 seats, Democrats would still control the house 224-210 at the moment. While it was certainly not beneficial to have so many sitting members retire simultaneously, it does not appear to be the main reason for the blue wave in the House.

So if retiring members were not the reason the Republicans failed to maintain control, what lead to the wave? Well for one, history. The presidents party has lost seats in 7 of the last 9 midterm elections. Midterms tend to be a time when the base of the party who lost the White House lash out, looking to take back power after their loss in the presidential election. Typically, this sentiment rolls over to the senate, but Republicans benefitted from a historically advantageous senate map in 2018. While red states like Tennessee and Mississippi became more entrenched due to their senate races, states like California and New Jersey offered prime opportunities for Democratic House candidates. The ability to capitalize on these opportunities in blue states is the main reason Democrats were able to flip the House, while Republican vacancies opened the door for a handful of additional pickups.