Long-simmering anxieties about an AI bubble were suddenly set off by a single election outcome.
A sweeping Democratic victory in the US midterm elections should have been a signal that risk had been cleared—and the stock market initially reacted that way. But within less than 24 hours, Wall Street completed a dramatic reversal from celebration to panic. On Thursday, the Nasdaq 100 posted its largest single-day decline since March 2020, erasing $2.3 trillion in market value in one session; measured from its October 6 high, total US stock market losses have now reached $5.7 trillion. The VIX fear index surged from 16.6 points to nearly 28 points, marking one of the most violent volatility events on record starting from the calmest possible baseline.
The trigger was the market's repricing of the Democratic Party's policy stance—particularly its deep skepticism toward the massive expansion of AI data centers. This political variable, layered on top of already highly crowded AI trade positioning, created a rare scene of retail investors, hedge funds, and quantitative strategies all stampeding at the same time. What made this sell-off so devastating was that it gave almost no one time to react—from retail investors fleeing first, to hedge funds following, to quantitative strategies mechanically unwinding—all completed within just a few hours.
Election Night: From Celebration to Confusion
On Tuesday night, the Democrats' landslide victory exceeded expectations. According to a Wall Street Journal report, Ben Emons, head of an investment research firm, sat in his Manhattan office from 9 p.m. to midnight as his phone rang almost nonstop. He took client calls while doing push-ups beside his desk to stay alert. "People were caught flat-footed," he said. "This was a genuine shock event."
At the time, stock index futures dipped during early vote counting, but as the Democratic victory became clear and Trump publicly said he would accept the election results, futures quickly turned positive. George Mateyo, chief investment officer at Key Private Bank, watched the live coverage at home while texting colleagues. His judgment was that the risk of a fierce post-election dispute had dissipated, and the market should welcome that.
That judgment was confirmed on Wednesday morning. "Real economy" sectors such as construction and retail surged, and the Dow recorded its best single-day performance since April. Wall Street briefly breathed a sigh of relief—believing that election uncertainty had been written off once and for all.
However, this rebound quickly proved to be a false breakout.
Retail Investors Flee First, Panic Spreads on Social Media
Thursday's sell-off was first ignited by retail investors.
In the first half hour after the open, the Nasdaq plunged rapidly, and individual investors' net selling reached historic levels. According to data from research firm Vanda Research, Thursday's single-day retail net selling was second only to the two trading days during the March 2020 COVID shock. JPMorgan's market intelligence desk noted that retail selling volume deviated from normal levels by more than three standard deviations.
"I started working at 7 a.m.," said Raphael Monges, a Columbia University engineering graduate student and member of the Columbia Options and Futures Trading Club. "I saw the market open, the Nasdaq was falling fast, then the S&P. The Nasdaq was insane—all the AI stocks were getting hammered. My phone started buzzing nonstop, everyone was staring at their stocks, all red."
Kevin Xu, a San Francisco investor and content creator, glanced at the market at 10:30 a.m. Thursday and froze. The Nasdaq was already down 4%, and his retirement account had lost six figures overnight. "There's nothing you can do," he said. "You just watch." In his social media feed, other retail investors posted memes, vented in all caps, and some even shared mental health hotline numbers.
Joel Rieger, a 50-year-old retail trader in California, did not adjust his positions during the turmoil. "Yesterday's portfolio took a heavy hit, red everywhere," he said. "It's going to hurt in the short term."
Hedge Funds Follow, Institutional Selling Meets No Buyers
The retail exodus was only the opening act. As market direction became established, hedge funds and long-only asset managers joined the selling, while almost no buyers appeared on the other side.
According to a Bloomberg report, "Institutional investors have stepped away, while retail and systematic strategies are aggressively selling," Vanda global macro strategist Viraj Patel wrote in a note. "This kind of flow dynamic is extremely rare outside of genuine market stress periods."
Ron Adler, co-head of global equities high-touch trading at JPMorgan, witnessed the entire session from the cash trading desk—volume that day surged 50% above normal. "Part of what we saw was portfolio pain and indiscriminate selling," he wrote in a note to clients. "The candor of today's flows was directionally reasonable, but the magnitude was staggering."
According to Goldman Sachs Prime Brokerage estimates, fundamental long/short hedge funds lost 1.3% on Thursday alone, a two-standard-deviation event; tech-focused funds fell more than 4%, nearly erasing their year-to-date gains. Momentum strategies suffered a 3.7-standard-deviation loss. Morgan Stanley data showed that the decline in total hedge fund leverage from its June peak was the largest in over a decade.
Quantitative Unwinding Takes Over, Systematic Selling Pressure Self-Reinforces
Once the market decline was established, a series of quantitative trading mechanisms were triggered, pushing selling pressure to a new magnitude.
Charlie McElligott, managing director of cross-asset strategy at Nomura, estimated that options dealers' negative gamma exposure during Thursday's session was roughly $7 billion per 1% market move—meaning for every 1% decline in stocks, dealers needed to sell an additional $7 billion in equities to hedge. Meanwhile, volatility-control funds needed to sell about $61 billion in stocks, of which $25 billion came from unwinding not yet completed on Wednesday; leveraged ETF closing rebalancing would contribute another roughly $47 billion in selling.
Trend-following quantitative funds (CTAs) were also retreating in tandem. According to Vanda estimates, CTAs sold a combined roughly $13 billion in S&P 500 and Nasdaq futures, with positioning dropping to near historic lows.
Barclays estimated that volatility-control funds cut equity exposure by 30 percentage points in a single day—the largest single-day reduction since the February 2020 COVID shock. "Conversations with clients tell me they have a stronger incentive to reduce risk further at this point," McElligott wrote. "The feedback theme is: preserve whatever little year-to-date gains remain, and survive into next year's new capital and new risk cycle."
At 3 p.m., the Nasdaq was down 4.5%, and some traders were still hoping for a last-hour rebound. Instead, selling intensified further, and the S&P 500 closed near its session low, recording its largest single-day decline since April of last year.
AI Sector Liquidated, Damage Concentrated and Severe
The destructive force of this sell-off was highly concentrated in AI-related sectors.
Sub-sectors such as memory chips, optical networking, data centers, and AI semiconductors fell 12% to 15% in a single day—extreme moves of five to six standard deviations. About a dozen AI stock baskets all posted their worst single-day performance since ChatGPT's launch in November 2022. The hardest-hit memory and optical communications baskets have been cut in half from their June highs, exceeding any pullback in the past four years.
As of Thursday's close, 57% of Nasdaq 100 constituents had fallen more than 20% from their highs—a proportion even higher than when the index itself entered bear market territory in March 2022.
What made this crash seem especially dramatic was partly that it erupted almost out of calm. The VIX was just 16.6 points at Thursday's open, below its one-year average; by the close it was near 28. Since 1980, the S&P 500 has fallen more than 2% the day after rising 1.5% only 48 times, almost all during bear markets or crises.
Political Shock Compounds Old Worries, AI Narrative Faces Repricing
The market's violent reaction reflects investors' deep anxiety about the AI investment thesis.
Even before the election, the market had doubts about the sustainability of the AI trade: tech giants' capital expenditures were continually swelling, cash reserves were shrinking, and debt was piling up on data center operators' balance sheets. The Democratic victory added a new layer of political risk—the Democratic Party's strong opposition to data center expansion, especially in Texas, Ohio, Georgia, and other states that have become key battlegrounds for data center construction, casting a shadow over the prospects for AI infrastructure buildout.
Bank of America analyst Michael Hartnett noted that among surveyed voters, as many as 76% opposed new data centers being built near their communities—a serious obstacle to AI infrastructure expansion.
Matt Rowe, a senior portfolio manager at Man Group, said the election results provided "quantifiable evidence that there is genuine public aversion to data center construction," which "begins to change my assessment of the probability these projects get built." "All else equal, these projects will take longer to advance and cost more."
Joe Gubler, a portfolio manager at Causeway Capital Management, noted that "there will always be losers, and not everyone betting on capex can be a winner."
On the other side, investors who exited early avoided the storm. Jeff Muhlenkamp had nearly cleared all AI holdings from his fund before the crash; his $275 million portfolio was essentially flat since November and has outperformed the S&P 500 for the year. "We sold what was expensive and popular, and bought what was cheap and forgotten," he said. "When momentum turns, we benefit."
The Market Searches for a Way Out
As the AI trade was liquidated, investors are looking for new safe havens—but the path is not smooth.
Even before the election, money had begun rotating into more lowly valued defensive sectors such as utilities and consumer staples. In October, growth stocks underperformed value stocks by 10 percentage points, the largest monthly gap since 2001. However, Thursday's crash showed that these new favorites also failed to withstand the shockwave from the tech sell-off.
Some investors had positioned early and escaped unscathed. Fund manager Jeff Muhlenkamp had already liquidated almost all AI holdings before the crash; his $275 million portfolio was basically flat in November and has outperformed the S&P 500 year-to-date. "We sold what was expensive and hot, and bought what was cheap and forgotten," he said. "When momentum turns, we benefit."
On Friday, chip stocks rebounded first, with the Nasdaq 100 briefly recovering more than 2.6%, but major indexes still ended the week lower, with the S&P 500 down 2.68% for the week. Sinisa Sorgic, a veteran trader at Bright Trading, shorted TSMC's US-listed shares that day but was "burned" as the stock rebounded more than 7.8% intraday. He summarized the week's feeling: "Yesterday was a bloody battle. The market is so crazy now that I don't dare go all-in to buy the dip."
Divergence has already emerged. Mateyo of Key Private Bank believes state-level regulations will delay but not stop data center construction, and public skepticism about AI may gradually fade as actual usage spreads. Casaletto of Wellington Management is more cautious, believing the trend of slowing AI expansion is already established.
Whether this storm is a violent shakeout in the middle of an AI bull market or the beginning of a deeper cyclical shift, Wall Street has yet to reach a consensus. But one reality is already clear: when political winds and crowded positioning turn at the same time, the cushion the market can provide is far thinner than imagined.
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