NEW YORK (Reuters) - Shares of Nvidia ( NVDA ) and other Big Tech stocks have helped power the markets run to record highs this year. Their recent wobble is making investors nervous.

A tumble in the chipmaker's shares shaved $279 billion off Nvidia's ( NVDA ) market capitalization on Tuesday, the single largest one-day decline in market value on record for a U.S. company. The stock was rebounding on Wednesday, rising 1% in late morning trading.

Whether the steep fall is due to investors becoming more cautious towards the artificial intelligence trend that supercharged market returns this year or worries over the health of the U.S. economy, more trouble for Nvidia ( NVDA ) and other Big Tech stocks would likely spell trouble for the broader markets.

Nvidia ( NVDA ) - along with Apple, Microsoft, Amazon and Alphabet - currently make up more than a quarter of the weight in the S&P 500 and over a third of the Nasdaq 100. Nvidia ( NVDA ) alone had comprised 23% of the S&P 500's year-to-date total return of 19.5% as of the end of August.

Further losses in their shares would likely hurt those indexes, which hit record highs in July, unless stocks in other sectors of the market pick up the slack.

"When you look at Nvidia ( NVDA ) as a market leader, it's not holding up despite very strong profits," said Jason Teh, chief investment officer of Vertium Asset Management in Sydney. "There's an old saying - if the troops can't follow the generals, it's a warning sign."

Nvidia's ( NVDA ) quarterly forecast last week failed to meet the lofty expectations of investors even as second quarter revenue and profit topped estimates.

"Those earnings last week were fine; they exceeded expectations," said Steve Sosnick, market strategist at Interactive Brokers. "But the magnitude of the beats is shrinking quarter by quarter and that's not lost on investors."

Index funds that track the S&P 500, Nasdaq 100 and other benchmarks also stand to suffer if Nvidia ( NVDA ) slides, because of the stock's increasingly heavy weighting in these indexes. The chipmaker has even more sway in more narrow indexes and exchange traded funds that focus on technology and semiconductor shares.

Even with its recent slide, Nvidia ( NVDA ) shares have more than doubled in 2024, as of Tuesday's close, and the stock remains the best year-to-date performer in the S&P 500. Shares of the AI heavyweight are up a whopping 800% since October 2022.

Nvidia's ( NVDA ) ascent has helped drive the valuation of the broader S&P 500 technology sector higher, causing some concerns about a bubble in tech stocks. But the sector's forward price-to-earnings ratio remains well below levels reached in 2000, during the dot-com era.