US midterms could reshape financial markets, but Treasury yields, oil prices and the Iran war may prove more consequential for investors.
The election comes at a fragile moment for financial markets, making its potential implications particularly relevant to investors. The S&P 500 closed at 7,580.07 on Friday, October 30, down 1.82% on the day. The Nasdaq Composite fell 2.86% to 25,437.00 as disappointing technology earnings revived doubts about spending on artificial intelligence (AI). Strategist notes, forecasts and Friday's prices suggest that a Democratic House is largely expected, so the larger market risks lie in an unexpectedly close or contested count and in forces the election will not change, chiefly the Iran war's effect on oil and the level of U.S. Treasury yields.
Several aspects of the outcome remain uncertain, including when the closest Senate races will be called, whether legal challenges in Alaska and California will delay certification, and how markets will respond to a split Congress compared with a Democratic sweep. Morgan Stanley warned that a close election or delayed results could cause short-term volatility, while a broader disruption to election integrity could cause greater turbulence.
Despite the uncertainty surrounding the final count, polling models increasingly favour Democrats in the contest for the House. Decision Desk HQ's model gave Democrats an 83% chance of winning the House as of October 31, with a projected 241 seats. The same model put Democratic odds of winning the Senate at 63%. A forecast by Harvard University political scientist Gary King and colleagues estimated a 95% chance that Democrats take the House, and cited a RealClearPolitics generic-ballot average of D+8.4 on October 31.
While the House outlook appears increasingly settled, the Senate contest remains considerably less predictable, a distinction also reflected in investor surveys. Kyle Kondik, managing editor of Sabato's Crystal Ball at the University of Virginia Center for Politics, said a big Democratic generic-ballot lead "suggests that the House is almost certain to flip to Democrats," but added that the Senate "is much more up in the air." Wolfe Research found that 96% of 138 investors it surveyed expected Democrats to win the House, according to an October 27 report. Wolfe itself put the chance of a Democratic Senate at 49%.
Record early participation has not eliminated uncertainty over when the final results will be certified. Pending legal disputes in several states could further complicate the certification process. In Alaska, U.S. Attorney Michael Heyman said on October 30 that a criminal investigation into how a second candidate named Dan Sullivan entered the Senate race is "ongoing." The Justice Department has asked a federal judge to block quick certification if Republican Sen. Dan S. Sullivan loses to Democrat Mary Peltola by a margin that could reflect voter confusion. Peltola's campaign and state election officials have asked the court to dismiss the suit, and Peltola has denied any involvement in recruiting the second Sullivan.
California presents a separate dispute over ballots. A federal appeals court on October 30 rejected in a 2-1 decision the Justice Department's demand that the state set aside ballots from 20,000 suspected noncitizens. The department has said it would appeal to the U.S. Supreme Court. Past audits have found noncitizen voting to be very rare.
Beyond their potential to delay certification, these legal disputes highlight a broader question for investors: how a change in congressional control could reshape fiscal policy, government spending and regulatory oversight. Analysts expect a divided government to produce legislative gridlock, particularly because Trump retains his veto power, according to a review of client notes published on October 30. TD Securities wrote on October 20 that "a blue wave scenario has become our base case." Piper Sandler, analyzing Congressional Budget Office data, projected that Democratic proposals "would add $5 trillion to the deficit over the coming decade," an estimate that assumes tariff repeal and reversed cuts to Medicaid.
Historical market performance provides a useful, although imperfect, benchmark for assessing the implications of divided government. Since 1974, the S&P 500 has averaged a 5.7% return in the three months after a midterm election, rising in 11 of 13 cases, according to an analysis by Michael Townsend, managing director of legislative and regulatory affairs at Charles Schwab. Over six months the average was 12.4%, positive in all 13 cases. LPL Financial Chief Investment Officer Marc Zabicki attributed the post-election gains to declining uncertainty, adding that "the important catalyst may not have been which party won or lost."
This year's starting point weakens that historical comparison. According to Morgan Stanley's analysis, the S&P 500 has gained about 23% on average in the calendar year after midterms under a Republican president when Congress is split. The firm also pointed out that equities have already outperformed the typical second year of a presidential term, which could leave less room for gains. The brokerage Emkay Global Financial Services noted that U.S. equities had risen about 12% over the previous six months. It also cited a rise of about 61% in Brent crude prices.
The most immediate market consequences of the election could materialise across key sectors, including healthcare, energy and technology. In Zabicki's view, Democratic control could bring attention to Medicaid funding and Affordable Care Act subsidies, with hospitals and managed-care providers with Medicaid or exchange exposure among potential beneficiaries. Traditional energy producers could face more oversight. Large technology companies and AI infrastructure providers could face greater scrutiny over electricity demand and data-center expansion, he added.
Energy and technology shares carry a particular risk after strong gains this year. Morgan Stanley cautioned that headlines about regulatory scrutiny or cuts in government support could prompt pullbacks in those sectors even when longer-term earnings prospects are unchanged. TD Securities also predicted that a Democratic Senate could ease concerns about the Federal Reserve's independence, given the Senate's role in confirming new Fed governors.
The implications for Federal Reserve independence extend beyond equities and into the Treasury market, where rising yields remain an important consideration for investors. The 10-year Treasury yield ended October 30 at 4.94%, down from 5.24% on October 1, according to Treasury Department data. The 2-year yield was 4.56% that day, compared with 4.78% on October 1. The Cboe Volatility Index closed at 19.42 on October 30, up 12.91% from the previous session.
Bond investors also face fiscal questions that the election will not resolve. The International Monetary Fund's global markets monitor noted on October 30 that the 10-year yield was up almost 110 basis points since February 27, the day before the Gulf war began. A change in Congress "won't necessarily bring substantially lower rates or a lasting boost for bonds," Morgan Stanley wrote. The Bipartisan Policy Center expects the debt limit to be reached between late winter and mid-summer 2027, according to the October 30 review of analyst notes.
Yet neither a change in congressional control nor the prospect of fiscal gridlock addresses the immediate geopolitical risks facing global markets. The Iran war, in particular, remains a more consequential variable for international investors. Morgan Stanley judged that an end to the war before November 3 appears increasingly unlikely. Its research estimates it could take about four months after the Strait of Hormuz reopens to restore 75% of lost Middle East oil production. West Texas Intermediate crude futures rose 0.9% to $102.95 a barrel on October 30.
Asian markets felt the technology sell-off before Wall Street's Friday session. Japan's Nikkei 225 closed at 63,290.11 on October 30, down 2.12%, with technology stocks accounting for most of the day's decline. The International Monetary Fund observed that most global markets sold off that day as oil rose on worries about escalation in the Middle East.
India, however, moved against that regional trend, and its case shows how the election reaches emerging markets indirectly. The BSE Sensex rose 0.42% to 74,459.53 on October 30, and the Nifty 50 gained 0.51% to 23,053.10, as information technology and pharmaceutical shares advanced. Foreign institutional investors were net sellers of Indian equities worth ₹34,843 crore in October, according to National Securities Depository Ltd. data cited in a weekly market preview.
For Indian investors, the main channels are oil and U.S. yields, not the composition of Congress. Emkay expects the election's implications for India to be 'more geopolitical than directly market-related', with the dollar, U.S. bond yields, global risk appetite and crude oil serving as the key variables. "We contend that oil prices are unlikely to decline after the midterms," the brokerage wrote. The firm assigned a 60% probability to Democrats winning both chambers, according to a summary of the report.
US trade policy presents another potential source of economic implications for India following the election. Here, however, analysts anticipate more continuity than immediate disruption. A Democratic Congress could increase scrutiny of tariffs, but the president retains considerable executive power over trade, Emkay argued. An ICICI Bank report concluded that the more immediate effects of Democratic control would likely be "increased oversight, legislative disputes and greater uncertainty for businesses, rather than an automatic dismantling of the current tariff framework."
Taken together, the polling and Friday's prices point to a market that has largely absorbed a Democratic House and still treats the Senate as open. Nor do they establish whether a clean electoral outcome would produce the post-midterm equity gains seen historically. This year's market rally, a 10-year Treasury yield near 5% and oil above $100 a barrel create a markedly different starting point. The vote count beginning Tuesday night, along with any legal delays in Alaska or elsewhere, will test the first assumption. Oil and the AI-earnings cycle will test the second. If Congress changes hands and Hormuz stays closed, will investors treat gridlock as relief, or will the energy shock continue to set the price of risk?
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