As ballots start to hit mailboxes ahead of the November midterms, Democrats are finally feeling some long-awaited electoral optimism. But to build a coalition that can defeat MAGA politics for good, the party will have to win back voters it's lost. In her new book, “How to Eat An Elephant,” Sarah Longwell, founder and publisher of The Bulwark, gives readers a blueprint to do just that. In a live…