How Janet Mills was boxed out of the Maine Senate race by Graham Platner's rise

By the time Maine Gov. Janet Mills launched her Senate campaign in October, Graham Platner was already drawing large crowds and raising impressive amounts of money.

The then-77-year-old governor was running for office at a time when many in her party were agitating for generational change. But Mills supporters – including Senate Minority Leader Chuck Schumer – thought she could prevail with a pitch for electability based on her statewide name recognition, backing from Senate Democratic leadership and a tidal wave of opposition research on Platner.

They were wrong, and on Thursday, Mills ended her campaign weeks before the June 9 primary...