D emocrats are pressing Senate Minority Leader Chuck Schumer, 75, to stay out of future primaries after his 78-year-old pick for Maine’s Senate race dropped out this week, Politico reported . On Thursday, Gov. Janet Mills announced that she would drop out of the Democratic primary, essentially clearing the field for insurgent progressive candidate Graham Platner to become the party’s nominee to challenge Republican Sen. Susan Collins. Schumer had backed Mills , the two-term governor of Maine, for the marquee race involving the only Republican representing a state with a majority that voted for Kamala Harris. But Mills consistently polled behind Platner despite a litany of controversies around the oysterman regarding his use of a slur for people with disabilities, and his comments on Reddit from more than a decade ago about Black people not tipping at restaurants and about sexual assault in the military.…