Stock market today: Dow, S&P 500, Nasdaq wobble in countdown to Nvidia earnings report

US stocks wavered on Wednesday as investors counted down to Nvidia's (NVDA) highly anticipated earnings report, seen as a pivotal test for the tech-driven summer rally. The Dow Jones Industrial Average (^DJI) hovered above the flatline, while the S&P 500 (^GSPC) fell below the flat line. The…