On Thursday, the Philadelphia semiconductor index lost 12.3% of its value in a single session, its worst day since March 2020. Nvidia fell more than 9%. AMD dropped 17.3%. Two days earlier, Democrats had won control of both chambers of Congress, and Wall Street spent the rest of the week trying to work out what that meant for the machines that power artificial intelligence.

A Market That Shrugged, Then Flinched

The midterms were held on November 3, and the first reaction was calm. Markets rose on Wednesday in their best day in three months, according to the Associated Press. Some outlets described the move as investors largely looking past the results.

Then came Thursday. The S&P 500 fell 4.4%, or 334.89 points, to 7,353.73, its worst day since April 2025. The Dow shed 1,833.06 points to close at 51,523.06. The Nasdaq composite dropped 5.5% and finished 11.9% below its October record, which is the technical definition of a correction.

The damage was not confined to chipmakers. CoreWeave fell 9.8% and GE Vernova, a supplier tied to the power demands of data centers, slid 7.5%. Overseas, South Korea’s Kospi lost 5.3% and Japan’s Nikkei 225 fell 1.8%.

The Data Center Question

The explanation most often offered by the AP, CBS News and Capital Economics is political. Democratic wins, they said, raised the odds that governments could force pauses in data center construction, on top of months of worry about borrowing costs and stretched valuations. That is the market’s interpretation, not a proven cause, and the AP itself noted that over the long run stock prices follow profits and interest rates far more than they follow who controls Washington.

Still, the concern is not hard to understand. The AP reported that AI data center construction drives a large share of U.S. economic growth. A slowdown in building would mean fewer chip orders, and less demand for electricity and the services that surround the industry.

Joe Maher, a markets economist at Capital Economics, told CBS News that the immediate risk was restrictions that “slow the pace of the AI infrastructure buildout.” Liz Ann Sonders, chief investment strategist at the Schwab Center for Financial Research, put the broader uncertainty differently, saying that markets are working out “what the speed limit is for this buildout.”

Voters seemed to have the issue on their minds as well. An NBC exit poll reported by Time, and a CNBC poll, found that 56% of voters called AI and data centers a crucial or major factor in their decision.

Texas Offers a Preview

The clearest example of the policy risk came from Texas. Democrat Gina Hinojosa won the governor’s race after pledging a moratorium on new data center approvals until the legislature passes new rules. Her plan, as reported by the Texas Tribune, would last until lawmakers meet in January. She is scheduled to be sworn in that month.

Federal action faces a steeper climb. Fox Business noted that President Trump retains veto power over any legislation Congress might send him. On the investor side, venture capitalist Chamath Palihapitiya offered a blunt view during an election livestream on the All-In podcast: “the only way to sink the AI trade is to sink the data centers.”

Earnings and Jobs Data Added Pressure

Politics was not the only thing on traders’ screens. Qualcomm and Arm both reported results after the close on Wednesday that investors viewed as mixed. Qualcomm’s handset chip revenue fell 26% to $5.14 billion in its fiscal fourth quarter, according to Reuters.

On Friday, the Bureau of Labor Statistics reported that employers added 165,000 jobs in October, with unemployment at 4.1%. Schwab put the consensus forecast at 65,000, so the report landed well above expectations. A strong labor market can complicate the rate outlook, and borrowing costs were already one of the anxieties hanging over the AI trade. The BLS release carries the full employment figures.

The bond and oil markets were moving too. The 10-year Treasury yield eased to 4.84% from 4.90% on Thursday, while Brent crude rose 3.9% to $98.29, with the U.S.-Iran war continuing to push up oil prices and inflation. The Bank of England also raised rates on Thursday for the first time in three years. Schwab, citing Bloomberg, reported that the high-yield credit spread widened by 15 basis points, a jump matched on only two other days in the past year.

A Partial Rebound, but a Rough Week

Friday brought some relief. The S&P 500 rose 0.32% to 7,376.86 and the Nasdaq climbed to 24,579.43, while the Dow slipped 237 points to 51,285.73, according to Reuters.

The weekly numbers still tell the story. The Nasdaq fell 3.4%, the S&P 500 fell 2.7% and the Dow fell 0.9%. It was the Nasdaq’s fourth straight weekly decline, and the S&P’s drop was its worst week since the April 2025 tariff shock.

The comparison to that spring is not incidental. The last sell-off of this size followed the “Liberation Day” tariffs, a deliberate and sweeping policy change. This one followed an election, and the policy it is reacting to has not been written yet.

Context: A Long Run, Now Interrupted

The AI trade has been rewarded handsomely. Nvidia had gained roughly 39%, 171% and 239% over the last three years, but after Thursday it was down 2.6% for 2026. Schwab reported that the stock sat more than 25% below its October 6 high, while the Nasdaq-100 was about 15% below its own October peak.

That backdrop is part of why the reaction was so sharp. When a sector has priced in years of uninterrupted expansion, even the possibility of a speed limit can move prices quickly.

What to Watch Next

The coming week offers several tests. October consumer price data arrives Tuesday, November 10, the same day CoreWeave and Rigetti report earnings after the close. Cisco and Applied Materials report Thursday, November 12, and producer prices follow on Friday, November 13.

The larger test is political rather than financial. Whether Texas moves from campaign promise to enforceable policy in January, and whether other states follow, will say more about the future of the data center boom than any single trading session. For now, the market has told us it takes the risk seriously, even if no one yet knows how much of it will materialize.