US parties splurged on the midterms – but research shows the link between spending and success is weak

The 2026 US midterms set a record for campaign spending in a congressional election. According to OpenSecrets, a Washington-based non-profit organisation that tracks and publishes data on US campaign financing and lobbying, the Democratic and Republican parties are estimated to have spent nearly US$12 billion (£8.9 billion) between them. Both parties spend more in total on campaigning in presidential election years, as the chart below shows. But the latest figures represent a 26% increase in spending on congressional races compared with 2024. The Democrats accounted for 46% of the total amount spent in 2026, with 43% attributed to the Republicans. Independent candidates accounted for the other 11%. OpenSecrets data shows that “plutocrats”, a term used to describe people who hold social and political influence due to their wealth, largely back the Republicans. Democrat campaign spending, meanwhile, relies more heavily on smaller donations from large numbers of supporters. In the run-up to the 2024 US presidential election, for example, the top five campaign donors gave just over US$863 million to the Republicans. Elon Musk was number one, with a donation of almost US$292 million for the Republicans and nothing for the Democrats. Spending on US election campaigns (1998-2024) Billions of US dollars are spend on US election campaigns. Paul Whiteley, CC BY-NC-ND Mike Bloomberg, a US businessman and the former three-term mayor of New York, was the most generous donor to the Democrats in the same cycle. He donated nearly US$61 million to the party, while giving US$1 million to the Republicans. The final spending data for 2026 is yet to be published. But this trend looks to have continued. According to the BBC, Musk made the largest donation of the contest, spending almost US$450 million in support of Republican candidates. By European standards, the spending on US election campaigns is enormous. Total spending on the UK’s 2024 general election was £94.5 million, a figure dwarfed by Musk’s contributions to the Republicans. But does election spending have any real effect? Does campaign spending win votes? The scale of the defeat for the Republicans in the 2026 midterms was unusual. Democrats took control of Congress and made gains in states that have been Republican for decades, including Kansas and Texas. This raises the question of whether it was discontent with Donald Trump’s second term and the Republican Congress, as opposed to campaigning by the Democrats, that had more effect on the result. A study from 2017 by American political scientists Joshua Kalla and David Broockman sheds light on this debate. They reviewed 49 different field experiments on the effects of election campaigning in the US and concluded that “the effects of campaign contact and advertising on Americans’ candidate choices in general elections is zero”. They attributed much of this to partisanship, or the psychological attachment American voters have to political parties. This tends to override campaign messaging. If a voter is a strong Democrat, for example, they will probably ignore campaign messages from Republican candidates. Other research has also found evidence that the saturation of political messaging during campaigns can turn people off politics in general, not just specific elections. Researchers call this effect “media malaise”. Kalla and Broockman revised their conclusions slightly in 2023. Reporting the results of another experiment, they suggested there are “learning effects” in political campaigns – particularly for people who do not follow politics. Voters may acquire information through campaigns that could affect their vote, such as finding out a particular candidate has been involved in a scandal. But while acknowledging this can produce changes to the overall vote, they concluded that campaigning still has a relatively small impact on US election results. These findings are consistent with other research, including the media malaise hypothesis. There is a consensus in the academic literature on the weak impact of campaign spending on US elections. Campaign spending and House seats won by Republicans (1998-2024) There is little correlation between campaign spending in US elections and winning seats in the House of Representatives. Paul Whiteley, CC BY-NC-ND The second chart shows the relationship between campaign spending by the Republicans and the number of seats they won in the House of Representatives in the 13 US elections that took place between 1998 and 2024. It provides a rough guide to the effects of campaign spending in congressional elections. The conclusion is that overall spending on campaigns has no significant effect on the results. This is consistent with the work of Kalla and Broockman and others, and raises the question of why Americans spend so much on their elections if doing so has such little effect. The answer is that electoral competition shares characteristics with an arms race, where behaviour is driven largely by a fear of missing out. Candidates become anxious they will lose elections if their opponent campaigns and they do not. This is much like the nuclear arms race in the 1950s and 1960s, in which the US and Soviet Union overinvested in nuclear weapons to the point that they could destroy each other many times over. Campaign spending is not a complete waste of money. Many voters like to see the candidates they are voting for, while campaign work by candidates is expected by party activists. But the evidence shows that greater and greater spending has little effect on how people vote. The lesson here is that it is easy to overstate the influence of plutocrats on electoral processes. When the new US Congress takes office in January 2027, one of its first acts should be to curb the expense associated with these campaigns.