Wall Street took one of its sharpest drops in more than a year on Thursday, led by stocks tied to the buildout of AI data centers, according to the Chicago Tribune and the Associated Press. The S&P 500 fell 4.4 percent, its worst decline since the tariff-driven shock of April 2025, while the Dow Jones Industrial Average lost more than 1,800 points and the Nasdaq composite tumbled 5.5 percent.

The wipeout more than erased the market’s gain from the day before, which had been its best session in three months. The pressure on AI-related stocks came from multiple directions at once, but traders pointed to one fresh trigger: worries about possible moratoriums on data center construction following Democratic victories in this week’s U.S. midterm elections.

Investors have spent months questioning how the enormous capital spending on AI infrastructure will translate into revenue, and the election results added a political dimension to those doubts. Communities hosting data centers have increasingly pushed back on power demands and water use, and candidates in several states made utility bills and data center growth campaign issues. A Congress more inclined to scrutinize the industry raises the prospect of slower permitting and new local restrictions.

The sell-off rippled through markets far from Silicon Valley. Chicago’s exchange-traded fund complex, one of the city’s signature financial industries, saw heavy trading volume as investors repositioned, and the city’s pension funds and wealth managers are exposed through broad index holdings that have become increasingly weighted toward a handful of AI-linked mega-cap stocks.

Corporate spending plans are the other watch item. The data center buildout has been a tailwind for construction firms, electrical contractors and utilities across the Midwest, and any slowdown in announced projects would affect suppliers and hiring plans well beyond the tech sector.

Analysts cautioned that a single session does not end the AI investment cycle, noting that earnings at the largest cloud and chip companies remain strong. But Thursday’s decline was a reminder of how concentrated market gains have become, and how sensitive valuations are to any hint that the infrastructure boom, which has powered much of the index’s advance since 2023, might cool.

The composition of the decline told the story. Chipmakers, hyperscalers and the power and cooling suppliers feeding the data center buildout led the losses, while defensive sectors held up better. Trading desks reported heavy volume in index options as institutions hedged concentrated positions, and volatility measures spiked to levels unseen since the spring of last year.

The political dimension is new. Until this week, the principal risks priced into AI infrastructure were financial, whether customer commitments would hold and spending would pay off. Election outcomes that empower lawmakers skeptical of data center growth, particularly around power consumption and land use, introduce a regulatory risk that cannot be hedged with semiconductor forecasts. Utilities and municipal leaders in several states, including Illinois, have been debating how to charge hyperscale customers for grid upgrades without shifting costs to households.

Market historians note that sell-offs of this depth often mark the transition from indiscriminate enthusiasm to selective judgment, not the end of a buildout. The question for investors is which parts of the AI supply chain show durable earnings, and which were financing a construction wave that could slow.