U.S. Rep. Chellie Pingree won a fifth term representing Maine’s 1st District in Congress on Tuesday after a low-key race against Republican challenger Mark Holbrook. Pingree, a Democrat, was leading Holbrook 63 percent to 37 percent with 24 percent of precincts reporting, according to unofficial election returns. The Associated Press declared Pingree the winner of the race at 9:50 p.m. The incumbent Democrat had been widely expected to defeat Holbrook, a lesser-known political newcomer who campaigned on a conservative platform in a left-leaning district that includes Portland and southern coastal Maine. A progressive Democrat, Pingree was first elected to Congress in 2008 after eight years in the Maine Senate and three years heading the national progressive group Common Cause.