As the 2024 elections approach, the Republican Party holds the US House of Representatives with 220 members, and the Democratic Party holds the US Senate majority with 51 seats, including independents. In a new forecast using a political economy model, Charles Tien and Michael S. Lewis-Beck predict that the Democrats will lose one seat in the House, meaning the Republican Party will maintain control, and six seats in the Senate, which will shift control of the chamber to the Republican Party.

Pundits and pollsters, not to mention engaged American citizens, are currently focused on the outcome of US elections. While the lion’s share of attention is focused on the presidential race, it’s important to keep sight of congressional races. The results of these contests will determine the extent to which whoever becomes the 47^th president can implement policy. Systematic efforts to forecast such election outcomes mainly track public opinion polls and, to a lesser extent, betting markets or predictive models. In our 2024 work, we rely on a political economy model we have used to predict national congressional elections in past races. As Figures 1 and 2 show, going back to 2006 the model generally manages to forecast accurately which party will gain (or lose) control of the House and the Senate.

Table 1 – House seats prediction under political economy model

Table 2 – House seats prediction under political economy model

How we predict House and Senate outcomes

The model predicts well because of its attention to fundamental political and economic conditions, and how they influence who people choose to vote for. Elections to the House of Representatives are assumed to be referendums on how the president’s party has handled important political and economic issues. e.g., such as immigration or inflation. Institutional features also matter, whether it’s a midterm election (which 2024 is not). With respect to the Senate, we apply the same political economic theory, again with the inclusion of an institutional feature, namely the number of seats the president’s party has up for election (based on the specific electoral calendar of that body). When the data on these factors are analyzed statistically (over the 38 US congressional elections from 1948 to today), we find that in 2024 the Republicans are likely to hold the House and likely to gain a majority in the Senate.

Predicting the House outcome

The political economy model for the House aims to forecast the Seat Change in that chamber, i.e., how many seats will the president’s party—the Democrats— gain or lose? That forecast is based on three fundamental conditions: how the president is doing on the economy; how the president is doing on non-economic issues; and whether it is a mid-term election. Further, as forecasts, these explanatory factors must be measured in advance, which they are, using available data from government documents and the media (July 25, 2024). The relevant measures are as follows: income growth is 2.07 percent, presidential job approval is 38 percent, and it’s not a midterm election.

What do these numbers mean? The economy shows moderate growth, which means a plus for the Democrats. The absence of a midterm election is another plus for the Democrats (the usual midterm penalty, on average, here would involve a loss of 30 seats.) However, the June Gallup presidential job approval rating reaches only 38 percent, which indicates dissatisfaction across a wide array of non-economic issues. Summing these factors together gives the following prediction: 

2024 House Forecast = -1 (one seat loss for Democrats)

Thus, this forecast suggests that with 220 current members, and 218 needed for a majority, the Republicans will hold onto the leadership of the House.

By United States House of Representatives or Office of the Speaker of the House [Public domain], via Wikimedia Commons

Predicting the Senate outcome

Turning to the Senate, we first look at the same set of explanatory factors as for the House. Again, the analysis shows that, in the Senate, the Democrats can expect to benefit from the observed income growth and the absence of a midterm election. Further, as with the House, they will be harmed by the low presidential approval rating. But, in addition they also will be punished because of the number of seats they have up for election, which is large; the Democrats are defending 23 seats, while the Republicans are defending only 11. Summing up all these factors together gives the following prediction:

2024 Senate Forecast = -5.5 (~ 6 seat loss for Democrats)

This appears to be a large loss. However, given the context, this predicted loss of six seats is about par for the course. Looking at all 38 election years under study, the average net Senate seat loss, when the president’s party defends 20 or more seats is -5. Moreover, in this 2024 contest, three Democratic Senate seats are in states won by Donald Trump  in 2020 (Montana, Ohio, West Virginia). Further, there are no Republican Senate seats up for election in states won by Biden in 2020. Taking these circumstances into account, this apparently extreme forecast becomes less surprising. 

A likely Republican majority in both the House and Senate

These predictions for 2024 forecast Democratic losses. Currently, the Republicans control 220 seats in the House, and the Democrats control 212. Three seats are vacant, of which two were vacated by Democrats. Thus, the President’s party needs to pick up four seats from 214 to win the House majority. Across the capitol dome, the Democrats control 51 seats (with the three Independents who caucus with the Democrats, and one who does not (Sinema)), and the Republicans need to pick up two seats for outright control, or one seat and the presidency for majority control. Hence, it appears unlikely that the Democrats will be able to keep their Senate majority, and unlikely that the Democrats can achieve a majority in the House. Of course, there is uncertainty regarding these forecasts. Nevertheless, they are the “best bet,” out of other possible choices, within our political economy framework.

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