Maybe Mattis was one of the people Rosenstein consulted with on the 25th amendment. Trump’s tepid endorsement of Mattis and speculation that he may be a Dem indicate that his days are numbered.
Mattis is not exactly what his public persona leads most people to believe he is. He has gotten a lot of mileage out of the "Mad Dog Mattis" persona and some well-publicized, and admittedly cool, quotes from his military career.
He has always been, however, just as most generals are, a political animal. Those of us Freepers who followed his performance during what was known as the Haditha marines trial debacle saw him in a different light.
He was still a three-star when he was put in charge. He then proceeded to leave Col. Chessani, Sgt. Wuterich and the rest of his fellow marines twisting in the proverbial breeze in the face of a politically motivated JAG prosecution of their alleged war crimes. Shortly afterwards he received his fourth star.
He is a genuinely great war fighting general, but he's also a politically motivated creature of the swamp, as his record as SecDef and tepid support of his president's agenda demonstrates.