Graham Platner, a scandal-plagued Democratic Senate nominee whose insurgent rise had drawn comparisons to Donald Trump, ended his campaign on Wednesday after a rape allegation threatened to derail one of his party’s best chances of flipping a Republican-held seat. Platner, a Marine veteran, oysterman and political newcomer, won last month’s Democratic primary in the northeastern state of Maine to face Republican Senator Susan Collins in November’s midterm elections. His withdrawal gives Maine...