The ultra-left’s conquest of the Democratic Party continues apace, as extremists triumph over more centrist candidates in primaries across the country. The dynamic may be most visible in Maine, where Graham Platner drove old-line Dem Gov. Janet Mills out of the race before the primary even happened. Platner is as hard-left as they come: all out on gender extremism, pushing anti-Israel lunacy to the extreme (including publicly cheering antisemitic conspiracy theorists) and screaming about the rich despite his own ultra-privileged background. (And that’s to say nothing of his Nazi tattoo, or his bizarre non-political public posting history, with its paeans...