If disruption from the Iran war persists through the November midterm elections, higher petrol prices and inflation could lead Republicans to lose control of both the House of Representatives and the Senate, potentially with substantial losses. If the disruption eases and petrol prices retreat, Republicans could perform better than they currently are and would be favourites to retain control of the Senate, according to election analyst Adrian Beaumont.

Beaumont said the assessment was based on the fact that President Donald Trump’s net approval rating and the generic congressional ballot were more favourable to Republicans in early September, before the latest fighting began. The main indicators to watch before November are whether the disruption continues to affect household costs, whether economic conditions improve beyond the stock market, and whether polling errors again favour Republicans.

Trump’s approval ratings and views on the war

According to analyst Nate Silver’s aggregate of US national polls, Trump’s net approval rating is -19.7. Some 58.2% of respondents disapprove of his performance, while 38.5% approve.

Trump’s net approval was -20.4 in Beaumont’s August 12 article. It improved to -18.7 on September 4 before declining again. The current figure is lower than that of any previous president since Harry Truman at the same point in a term. Trump’s first term is the closest comparison, at -13.1.

Silver’s figures track Trump’s net approval on four issues. The rating is -12.2 on immigration, -26.1 on trade, -30.8 on the economy and -46.4 on inflation. Since Beaumont’s August 12 article, Trump’s ratings on trade and inflation have fallen by between two and four points, while his immigration rating has remained relatively stable. His economic rating improved before suffering another decline.

Silver also publishes an aggregate of US support for the Iran war. At present, 55.7% oppose the war and 35.6% support it, producing net support of -20.1. That is slightly lower than the -19.6 recorded in Beaumont’s August 12 article.

The November 3 midterm elections

All 435 seats in the federal House of Representatives and 35 of the Senate’s 100 seats will be contested in the November 3 midterm elections.

In the 2024 elections, Republicans won the House by 220 seats to 215 and the Senate by 53 seats to 47. Because Vice President JD Vance could cast a tie-breaking vote, Democrats need to gain at least four Senate seats to take control of the chamber.

Beaumont previously wrote that Republican gerrymandering means Democrats need at least a four-point advantage in the generic ballot to have a strong chance of winning the House. The Senate is more structurally favourable to Republicans because every state has two senators. Under a uniform swing, Democrats need a double-digit generic-ballot margin to win Senate control.

In Silver’s midterm election forecast model, the generic ballot gives Democrats a 50.8% to 42.7% lead over Republicans, an 8.2-point margin. The margin was 8.1 points in Beaumont’s August 12 article and had narrowed to 7.4 points on September 4.

Polls that screen for likely voters generally show larger Democratic leads than surveys of registered voters. Democrats are also more likely than Republicans to vote in lower-turnout elections such as midterms when Trump is not on the ballot.

Silver’s model gives Democrats a 57% chance of winning the Senate and an 86% chance of winning the House, unchanged from August 12. Democratic Senate prospects had fallen to a low of 50% on September 7, while their House prospects had declined to 81% on September 3.

Although a uniform swing suggests Democrats need a double-digit generic-ballot margin to take the Senate, Silver’s model makes them favourites with a margin of six to seven points. In the House, Democrats are favoured if they win the generic ballot by three to four points.

Democrats have effectively gained a House seat in Missouri after courts annulled a Republican gerrymander. The map had given Republicans a 7–1 advantage among the state’s eight House districts; Republicans now hold a 6–2 advantage instead. The Supreme Court’s decision concerning Missouri’s congressional map is among the relevant legal developments.

Democrats lead by between one and four points in Senate contests in Texas, Ohio and Alaska. In Iowa, Democrats and Republicans are tied at 45.8% each. Trump won all four states by double-digit margins in 2024, a factor that helps explain why Democrats are nevertheless slight favourites to gain Senate control. The 2024 state results are listed here.

In Michigan, which is held by Democrats, left-wing Democrat Abdul El-Sayed trailed Republican Mike Rogers by 1.6 points in Beaumont’s August 12 article. El-Sayed now leads by 2.9 points.

Beaumont identified two developments that could undermine Democratic prospects: a marked improvement in the economy for most Americans by November, rather than only in the stock market, and a systematic polling error that results in Republicans outperforming their survey numbers.

Economic data

The US August jobs report, released on September 4, was favourable news for Trump. The establishment survey recorded a gain of 162,000 jobs, while the June and July figures were revised upward by a combined 55,000. The revisions changed July’s result from a loss of 23,000 jobs to a gain of 21,000. The Bureau of Labor Statistics report provides the employment data.

In the household survey, the unemployment rate remained at July’s 4.1%. The labour-force participation rate and employment-population ratio each rose by 0.2 percentage points, reaching 61.6% and 59.1%, respectively. In July, the employment-population ratio had fallen to its lowest level since September 2021.

Although August showed an improvement, the US employment-population ratio remained well below Australia’s, which stood at 63.9% in July, according to Australian Bureau of Statistics data.

The August inflation report, released the following Friday, showed overall inflation rising 0.4% and core inflation increasing 0.3%. In July, the respective increases were 0.1% and 0.2%. Annual inflation rates were 3.4% overall and 2.4% for core inflation, according to the Bureau of Labor Statistics consumer price report.

Real hourly wages declined by 0.1% in August, while real weekly wages increased 0.2% because of a rise in weekly hours. Over the past year, real hourly wages have fallen 0.3%, but real weekly wages have increased 0.3%. The related real earnings data provide the wage figures.

July was the first month since January in which personal income exceeded expenditure, mainly because expenditure declined. The personal savings rate rose 0.3 percentage points from June to 3.0%, after falling each month from February through June. The figures are reported in the Bureau of Economic Analysis release.

The benchmark US S\u0026P stock market index gained 0.9% in the previous Friday’s session, ending a four-session losing streak. The S\u0026P was down 1.8% from its August 13 peak, but up 10.2% from its peak in the week before the Iran war began in late February. It was also up 16.2% from its lowest point during the Iran war in late March.

Adrian Beaumont is an Election Analyst (Psephologist) at The Conversation and an Honorary Associate in the School of Mathematics and Statistics at The University of Melbourne.

This article is republished from The Conversation under a Creative Commons license. The original article was published by The Conversation.