Wall Street is flirting with a record on Tuesday, as stocks zigzag under the market’s surface following mixed profit reports from UnitedHealth, General Motors and other big companies.The S&P 500 rose 0.5% and could top its all-time high set a couple weeks ago, even though slightly more stocks fell within the index than rose. The Dow Jones Industrial Average was down 288 points, or 0.6%, as of 11:45 a.m. Eastern time, and the Nasdaq composite was 1% higher.UnitedHealth Group tumbled 19.1% despite reporting a ...