Friday in response to Secretary of Defense Gen. James Mattis announcing his resignation, MSNBC analyst John Heilemann suggested on “Morning Joe” that a lot of people “think it would be best for the country” if President Donald Trump were not to finish out his term. “[Y]ou have this resignation, historic in the way that Joe suggested, that I think for a lot of Republicans in the Senate who looked at Mattis as the guardrail, as the — I hate the phrase adult in the room, I’m not going the use it because I think it kind of diminishes others who...