By Noel Randewich (Reuters) – Wall Street slid deeper into a bear market on Monday, with the S&P 500 and Dow closing lower as investors fretted that the Federal Reserve’s aggressive campaign against inflation could throw the U.S. economy into a sharp downturn. After two weeks of mostly steady losses on the U.S. stock market, the Dow Jones Industrial Average confirmed it has been in a bear market since early January. The S&P 500 index confirmed in June it was in a bear market, and on Monday it ended the session below its mid-June closing low, extending this year’s overall selloff. With the Fed …