Nothing in Donald Trump’s presidency has been as unbecoming as his exit. He is putting new strains on his beleaguered party, which has surely suffered enough.

It’s not often these days that you see a one-termer. The last of them was George Bush the elder, who was also not young when he was elected and seemed to have lost all his zeal for the job when the Cold War ended, the cause that defined his real mission for most of his very long life.