I seem to remember US politics being pretty divided in the 1990s, and I don't remember anyone disputing Clinton's victories at the ballot box.
Ditto for Nixon in the 1970s based on what I have read, won an election landslide but was a very divisive figure even pre-Watergate.
Reagan won almost every electoral college vote and was seen abroad by many people as some sort of Yankee cowboy actor.
He had his battles with a Democrat controlled Congress.
Elections and politics are divisive.
I think what is more novel here is that Trump may well divide the Republicans.