The Democratic Party’s pick for Maine senator suspended her candidacy on Thursday. Democratic Gov. Janet Mills, who entered the race as the establishment pick and assumed favorite, announced her campaign did not have the financial resources to continue. Mills’s exit less than six weeks before the June primary clears the path for populist candidate Graham Platner, now the presumed nominee, to face off against incumbent Republican Sen. Susan Collins in the November general election after the party worked to subdue Platner’s campaign. The Democratic Party’s decision to wade into the primary at all had reignited a criticism that the Democratic...