U.S. stock indexes opened higher on Tuesday, as voting began in a tightly contested presidential election, with traders girding up for volatile trading over the next few sessions until a winner is declared. The Dow Jones Industrial Average rose 40.9 points, or 0.10%, at the open to 41835.49. The S&P 500 rose 9.7 points, or 0.17%, at the open to 5722.43, while the Nasdaq Composite rose 70.7 points.