US Midterm Elections: What Could the Results Mean for the S&P 500?

With the US midterm elections just a day away, investors are watching closely to see whether Republicans can retain control of Congress or whether Democrats will regain ground. Beyond the political implications, the results could influence expectations for fiscal policy, government spending, trade, technology regulation and, ultimately, financial markets.

The US midterm elections take place on 3 November 2026 (4 November in Singapore). Republicans currently control the White House, the House of Representatives and the Senate, making control of Congress the key question.

History suggests that the president’s party often loses ground at the midterms. In 18 of the 20 midterm elections since World War II, the president’s party lost seats in the House. Current forecasts favour Democrats retaking the House, while control of the Senate remains a closer contest.

Why Do the House and Senate Matter?

The US Congress has two chambers: the House of Representatives and the Senate. Both play important roles in shaping legislation, but their responsibilities differ.

这 House of Representatives has 435 members, with seats allocated according to each state’s population. All seats are contested every two years, and a party needs at least 218 seats for a majority. Tax and spending legislation originates in the House.

这 Senate has 100 members, with two senators representing each state. Senators serve six-year terms, with approximately one-third of the seats contested every two years. In this election, 35 seats are up for grabs. A party generally needs 51 seats for a majority.

The Senate also plays a role in confirming federal judges and senior government officials, as well as approving treaties.

Since legislation generally needs approval from both chambers before reaching the president, control of Congress can determine how easily an administration advances its policy agenda. A divided Congress can create legislative gridlock, while unified control gives the governing party greater room to push through its priorities.

Why Do Midterm Elections Matter to Markets?

For investors, the election matters less as a political contest and more for what it could mean for government policy.

A divided Congress could make major changes to taxation and government spending more difficult to implement. Some market participants view this as potentially positive because fewer policy changes can reduce uncertainty and provide a more predictable environment for businesses and investors.

Historical market performance also offers an encouraging backdrop.

The S&P 500 has historically performed well following US midterm elections. In midterm election years, the index has delivered an average return of 14.3% over the six months from the end of October, compared with 3.7% in non-midterm years. The fourth quarter has also historically been the strongest quarter of the year.

However, historical averages are not a forecast. Interest rates, corporate earnings, geopolitical developments and economic conditions can all influence equity performance independently of election results.

Three Possible Election Outcomes and Their Market Implications

The balance of power in Congress could produce three broad scenarios, each with different implications for policy and financial markets.

1. Democrats Win the House, Republicans Retain the Senate

This outcome would create a divided Congress.

With Democrats controlling the House and Republicans retaining the Senate, passing new tax and spending legislation could become more challenging. The administration would also face greater scrutiny from the House, while Republicans would retain influence over judicial and senior government appointments.

For markets, the key question is whether legislative gridlock reduces policy uncertainty and provides a more predictable environment for businesses.

2. Democrats Win Both Chambers

A Democratic victory in both the House and Senate would give the party greater influence over the legislative agenda and government oversight.

The administration could face stronger resistance to its policy proposals, alongside greater scrutiny of government spending, appointments and regulatory priorities.

Technology investors may pay particular attention to this outcome, especially if it leads to tighter oversight of artificial intelligence, data privacy or the technology sector more broadly.

The key question is whether increased regulatory scrutiny and potential policy changes could affect the growth outlook for technology companies.

3. Republicans Retain Both Chambers

If Republicans maintain control of Congress, the administration would have greater room to continue its legislative agenda with fewer congressional constraints.

Policy continuity could provide some reassurance to investors, particularly in areas where businesses have been anticipating further government support or legislative action.

However, questions surrounding government deficits, tariffs and geopolitical developments would remain relevant.

For markets, the focus would be on whether policy continuity provides greater clarity or whether existing fiscal and trade uncertainties continue to weigh on investor sentiment.

Three Policy Areas Investors Should Watch

Regardless of the final outcome, three policy areas could have broader implications for financial markets.

1. Fiscal Policy and Government Spending

A Democratic-led Congress could place greater limits on deficit-expanding legislation and push for closer scrutiny of government spending.

If this translates into lower expectations for fiscal expansion, it could influence inflation expectations and demand for US Treasury securities. However, the impact on Treasury yields and the US dollar would also depend on the Federal Reserve’s monetary policy and the broader economic outlook.

2. Iran Conflict and Defence Funding

Congressional control could influence future decisions on funding for the Iran conflict and related military spending.

Any restrictions on additional funding could affect expectations surrounding the duration and intensity of the conflict. A move towards de-escalation could ease concerns over energy supply disruptions, potentially reducing pressure on oil prices and inflation expectations.

This could have knock-on effects on bond yields, the US dollar and broader market sentiment.

3. Artificial Intelligence and Technology Regulation

The technology sector will also be watching closely for changes in the regulatory environment.

A Democratic-led Congress could push for greater oversight of artificial intelligence, including data protection, competition and the use of AI technologies.

This comes at a time when investors are already questioning whether the significant capital expenditure by major technology companies and hyperscalers will translate into sustainable returns.

Any shift in regulatory policy or government support could influence sentiment towards technology stocks, particularly companies with substantial AI exposure.

What Should Investors Watch After the Election?

As the results come in, investors may want to focus on more than just which party wins.

• Control of the Senate: With the House expected to be the more likely chamber to change hands, the Senate result could determine whether the US ends up with a divided Congress or Democratic control of both chambers.

• Market volatility: Uncertainty ahead of major elections can contribute to short-term market volatility. Once results become clearer, investors may respond with a relief rally, although the direction will depend on how the outcome is interpreted.

• Policy signals: Developments involving tariffs, government spending, the Iran conflict and AI regulation could provide further clues about the policy direction and its implications for businesses.

• Corporate earnings and economic data: Beyond politics, company earnings, inflation figures and interest rate expectations will remain important drivers of the S&P 500.

Positioning for the Next Market Move

The US midterm elections could influence the policy environment, but the impact on equities will depend on how investors interpret the results alongside broader economic and corporate developments.

Historically, the S&P 500 has tended to perform well in the months following midterm elections. However, past performance does not guarantee future results, and investors should remain mindful of changing market conditions.

The key question may not simply be which party wins, but whether the outcome brings greater policy clarity or introduces a new set of uncertainties.

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