LEWISTON –– Voters flowed into four polling places Tuesday, driven by keen interest in a five-candidate mayoral race that has drawn statewide attention. Two candidates, Mayor Robert Macdonald, 68, and his progressive challenger Ben Chin, 30, have become the focal point of the race. Their candidacies have been viewed by some as a proxy battle between the Maine Republican Party, which has leaned heavily on a welfare overhaul agenda, and the Maine Democratic Party, which suffered bruising losses at the polls in 2014.