Nvidia, Palantir and other superstar stocks that surged to records in the mania around artificial-intelligence technology are under pressure again on Wednesday and dragging Wall Street lower. The S&P 500 fell 0.

The heaviest weight on the market was Nvidia, whose chips are powering much of the move into AI. It sank 3.5%.

Wall Street's main indexes were down on Monday, as investors awaited a raft of corporate earnings reports from major retailers for more signs about the state of the economy and the Federal Reserve's annual symposium in Jackson Hole.