I was just reading about how Grant would have likely been also assasinated if his wife had not made him reject the invitation for them on account of Mrs. Lincoln's hostility to her. Now I wonder, Booth had only a single shot pistol and a dagger and neither Grant nor Lincoln were exactly weaklings. Suppose Booth tries to get them both? In the confusion he kills Grant but Lincoln manages to get the knife away and one way or another Booth can't reload.
If Lincoln is alive and well and Grant dead how much difference does it make with from things IOTL? And how much difference from that if they both survive unhurt?
Just think, Andrew Johnson never becomes President, and maybe even if Grant also lives his still becoming President is butterflied away.
Does Grant have anything significant to contribute that he cannot if he is dead, or alive but never President?