So this article amused me - the bad things presidents and would-be presidents have said about each other! It fits in with the election season (any, not just this one)!
Here are some particular nasty things said about poor Lincoln:
When the Civil War exploded in 1861, ex-presidents Millard Fillmore and Franklin Pierce attacked Lincoln as a war monger and would-be dictator. Pierce was particularly vehement. He found fault with almost everything Lincoln did, calling one of his early decisions "an idle, foolish, ill-advised, if not criminal thing."
Bad as this is, it does not approach the nickname New Jersey Democrats fastened on Abe -- "the brainless bob-o-link of the prairies."
Or here are some on Richard Nixon:
John F. Kennedy called Richard Nixon "a filthy lying son of a bitch and a very dangerous man." Lyndon Johnson was even more harsh -- and prophetic. "He’s like a Spanish horse, who runs faster than anyone for the first nine lengths, and then turns around and runs backwards."