UBS said in a research note published Sept. 11, 2026 that the S&P 500 has gained an average 14.5% from the end of August through the end of March in midterm election years since 1950, with a median return of 16.4%. The period has typically started with choppy trading, with the index recording a median decline of 1.4% from the end of August through early October before recovering into year-end. UBS said midterm elections have historically resulted in the president's party losing an average of 25 seats in the House and three seats in the Senate, and that the incumbent president has lost control of one or both chambers in eight of the 19 midterm elections since 1950. The firm said current betting-market pricing pointed to Democrats having more than an 85% implied probability of taking the House, while Senate control was closer to 50-50 at the time of the report. UBS said the outcome could affect the policy outlook for taxes, regulation and other areas relevant to equity markets, while emphasizing that the near-term path for stocks is likely to depend more heavily on administration policies and corporate profit growth over the next six to 12 months.
UBS Group AGUBS research note on historical S&P 500 midterm-year seasonality and election policy outlook; no company-specific financial event
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