Key Highlights

● Seasonal research favored autumn of midterm years.

● October 2026 broke the playbook.

● A sharp turn against AI-related stocks drove the decline.

● The S&P 500 ended the month down about 71.5 points.

Seasonal research has long favored the autumn of midterm election years. A market report published September 23, 2026, cited work by one market strategist showing that October has historically been a strong month for stocks in midterm years, and that November ranks as the second-best month. One asset manager has found the fourth quarter of midterm years tends to be strong, and UBS (NYSE:UBS) has found gains are typical from September to year-end.

October 2026 broke that pattern for the S&P 500. The index ended September at 7,651.54 and closed Friday, October 30, 2026, at 7,580.07, a decline of about 71.5 points for the month.

The AI cash problem

The biggest reason was a sharp turn against AI-related stocks. A string of Earnings reports showed how much cash the AI build-out is consuming. Meta (NASDAQ:META) reported its first negative quarterly free Cash Flow since 2012. Alphabet (NASDAQ:GOOGL)'s third-quarter free cash flow was negative $9.1 billion, against expectations of negative $3.5 billion, and its shares had their worst day ever on Thursday, October 29, losing about $500 billion in market value.

Then came Intel (NASDAQ:INTC)'s warning of cash burn and Amazon (NASDAQ:AMZN)'s trailing 12-month free cash flow of negative $42.4 billion. On Friday, the S&P 500 fell 140.32 points, the Dow Jones Industrial Average lost 572.25 points to 51,770.31 and the Nasdaq Composite dropped 747.73 points to 25,437.00. The Nasdaq ended its worst month since March 2025, and the Nasdaq-100 lost roughly $2 trillion in Market Value in October, according to market data.

Because the largest technology companies carry so much weight in the S&P 500, their slide outweighed gains elsewhere.

A hawkish Fed and $100 oil

Interest rates added pressure. The Federal Reserve raised rates in September and held them steady at its October 27-28 meeting, but two officials dissented in favor of another hike. Futures markets now price in a December increase. Chair Kevin Warsh said: "But Inflation remains elevated." Data released Thursday showed headline and core PCE inflation at their highest levels since May, and a Wealth advisor said: "Today's data strengthens the case for another rate increase in December."

Oil climbed above $100 a barrel, with December West Texas Intermediate crude settling at $104.12 on Friday. Reports that the United States could resume strikes on Iran, tanker incidents in the Strait of Hormuz and a Ukrainian strike on a refinery in Samara all pushed prices higher. Higher energy costs feed inflation concerns and pressure companies that rely on fuel.

A reported $6.3 billion hack of Binance, which TRM Labs and Elliptic tied to North Korea, added to the risk-off mood late in the month.

Beneath the surface

The S&P 500's monthly loss masked broad strength. Nine of the 11 sectors gained in October, according to market data, led by energy, with health care, utilities and staples also posting strong gains. The Dow rose about 864 points for the month and the Russell 2000 edged up about 15 points.

One asset manager's own caution fit the month well: fundamentals "are more important indicators of future returns than the election calendar itself."

What to watch

November now carries the seasonal hopes. The midterm elections are on Tuesday, November 3, with Democrats widely predicted to win the House and the Senate more in doubt, according to market data. Apple (NASDAQ:AAPL) reports Monday, November 2, and the October jobs report arrives Friday, November 6. The Fed's December decision looms over all of it.