A shortage of at least 500,000 poll workers nationwide means many voters could face long lines, cranky volunteers, polling places that don't open or close on schedule and the chance that results won't be known until long after the polls are closed. Roughly 1.4 million people have been trained to serve as poll workers on Tuesday, about the same as four years ago, according to the U.S. Election Assistance Commission. But nearly 2 million will be needed to deal with expected heavy turnout, huge numbers of first-time voters and unfamiliar touch-screen machines in hundreds of counties. Desperate for workers, the...