Many know that Chapman University’s Presidential Forecast Model has accurately called the popular vote winner in 15 of the last 16 elections. We recently broadened our political outreach to include a forecast of midterm elections for the House of Representatives.
In our recently completed study, “A Model to Forecast Midterm House Elections,” which was published in Social Science Research Network, we identified the major socioeconomic and political factors that explain changes in House seats during midterm elections. An R-squared term in our principal forecasting equation suggests that it explains an impressive 88% of the variation in elected House seats.
In analyzing election results for the 19 midterm elections between 1946 to 2018, we found that a sitting president’s political party almost always experiences a net loss in House seats when compared to the previous midterm election four years earlier. As shown in Chart 1, the president’s party lost seats in every midterm election except in 1998 and 2002. Over the entire period, the average loss was 27 seats.
That loss of 27 seats was our starting point. If we found that an explanatory factor did worse than average, the loss in House seats for the president’s party would be greater than 27. But if it did better, the loss in seats would be lower.
We found, for example, that for every drop in the president’s Gallup poll of 1% below the average approval ranking for presidents between 1946 to 2018, the president’s party loses 0.9 seats. Since President Joe Biden’s current approval ranking of 42% is 9 points below the average Gallup poll ranking of 51%, our model suggests that the Democratic Party will lose an additional eight House seats over and above the average loss of 27 seats.
We also found that real GDP growth affects midterm election results. Specifically, we found that for every decrease of 1% in real GDP growth from the average results in the loss of about three House seats. The lower real GDP we are currently projecting this year of 1.9% versus the average growth of 2.5% translates to an additional loss of about two seats.
We were surprised to find that overall price changes, as measured by the CPI, had no measurable impact on midterm House election results.
Gasoline prices, however, were found to be highly significant in influencing voters. Since people are reminded virtually every day about the gas price per gallon at every gasoline station they drive by, voters are seemingly more upset about gas prices than overall inflation rates. In addition to finding that voters blame the presidential party for rising gas prices, we found that voters appear to credit the president’s party when gas prices fall.
During the three midterm elections that experienced the most significant declines in gas prices, the president’s party had its best showings (see 1, 2, and 3 in Chart 2). In fact, the only two midterm elections where the president’s party gained House seats (1998 and 2002) were during years when gas prices declined (see 2 and 3 in Chart 2).
But when gas prices increased the most during a midterm election year (37% in 1974), the president’s party lost 48 seats (see 5 in Chart 2). The second-highest year of increasing gas prices was in 2010 (19%) when the president’s party lost 64 seats (see 4 in Chart 2).
Our Anderson Center is projecting that the average price for a gallon of gas will increase 36% in 2022. Such an increase is 33.5 percentage points higher than the average increase of 2.5% during midterm election years. Since our model found that every increase of 1% in gas prices leads to a loss of 0.6 seats, a 33.5% increase above the average points to an additional loss of 20 House seats for the Democrats in November.
If these forecasted impacts occur, our study suggests that next month’s election will result in a loss of 44 Democratic seats from the 222 seats the party currently holds. That, in turn, suggests that Democrats would end up with 178 seats versus the Republicans’ 256 seats.
As a result, the current Democratic majority of 10 seats would swing to a 78-seat majority for the Republican Party (see Chart 3).
Of all 38 House elections since 1946 (midterms and presidential elections), a majority of 78 seats would not be unusual for Democrats. The Democratic party had even larger majorities in 14 other House elections, but a majority of 78 seats for the Republican Party would represent the highest majority it had ever achieved since 1946—even greater than the majority of 59 seats Republicans held after the 2014 midterm election when Barack Obama was president.
Our model sees a bigger pickup than others also making predictions. For example, the Cook Political Report predicts a GOP gain of 10 to 20 seats while the RealClearPolitics average suggests the Republicans will win six to 40 more seats. The FiveThirtyEight website says the Republicans have a chance to win up to 28 seats.
If we’re wrong in this forecast, we’ll present all of our excuses at Chapman’s 45th Annual Economic Forecast on Dec. 13. Hope to see you there.
