US stocks scored gains Monday on the eve of the presidential vote, with President Barack Obama and Republican challenger Mitt Romney locked neck-and-neck in the race for the White House. The Dow Jones Industrial Average gained 19.28 points (0.15 percent), finishing at 13,112.44. The broad-based S&P 500 advanced 3.05 (0.22 percent) to 1,417.25, and the Nasdaq Composite was the best performer, adding 17.53 (0.59 percent) at 2,999.66. After opening mixed, stocks eked out a positive finish ahead of Tuesday\'s election. The political uncertainty had kept market conviction corralled, \"along with continued uneasiness in the eurozone toward the fiscal challenges in Greece and Spain,\" Charles Schwab & Co. analysts said. A slightly disappointing reading on activity in the massive US services sector added to the market caution. The Institute for Supply Management reported its purchasing managers index for the nonmanufacturing sector dropped to 54.2 percent in October from 55.1 in September. Most analysts had forecast a decline to 54.5 percent. Caterpillar jumped 1.1 percent in the aftermath of superstorm Sandy that battered New York and New Jersey a week ago, leaving huge needs for reconstruction of homes and infrastructure. Insurers were under pressure -- Dow member Travelers Companies fell 0.7 percent -- and utility stocks continued to suffer: Exelon tumbled 2.3 percent and Con Edison shed 2.0 percent. Humana rose 0.4 percent after reporting third-quarter earnings above expectations and raised its full-year profit estimate. The health care company also announced an $850 million deal to acquire Metropolitan Health Networks, up 2.8 percent. Supporting the Nasdaq was Apple, up 1.4 percent after announcing Monday it had sold three million iPads in the first three days of its launch of the iPad mini and the fourth-generation model of its original format iPad. Bond prices rose. The 10-year US Treasury yield fell to 1.68 percent from 1.73 percent late Friday, and the 30-year dropped to 2.87 percent from 2.92 percent. Prices and yields move inversely.