Maine voters head to polls on Tuesday for closely watched primary election

All eyes on US Senate race as Graham Platner, embroiled in controversy, is set to advance as Democratic nominee

Voters in Maine head to the polls on Tuesday for one of the most closely watched primary elections in the country. The US Senate race has become a national fixation as Democrats try to unseat a longtime Republican with a political newcomer who has spent months under fire.

Graham Platner, 41, is set to advance as the Democratic nominee for the Senate, after his primary rival - the state's two-term governor, Janet Mills - suspended her campaign in April. The primary result will likely set up a months-long run-up between Platner, an oysterman and marine veteran with a groundswell of popularity and a mounting list of scandals, and Susan Collins, a 73-year-old Republican senator who has held the seat for nearly three decades.