Sign up for the Slatest to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily. As primary season enters full swing, we’re beginning to get a clearer picture of which states will play a key role this fall. None is more critical for Democrats’ hopes of retaking the Senate than Maine, where a damaged Sen. Susan Collins only recently announced that she’s running again. Democrats view Maine as a rare opportunity to flip a seat that’s a must-win for a future Senate majority under a potential Democratic president in 2029—or a central part of...