The seemingly sturdy U.S. stock market has begun to wobble. Its monthslong tech-driven rally may be running out of steam amid broader uncertainty about the U.S. economy’s outlook. On Tuesday, the S&P 500, one of the broadest measures of U.S. stocks, fell more than 0.5% and looked headed for its fourth-straight day of losses. The Dow Jones Industrial Average and the tech-heavy Nasdaq were also in the red. Heavier losses were likely prevented by so-called retail investors, like day traders, who