I came of political age in the '70s, watched Watergate unfold, can still remember where I was when we learned Nixon resigned; the Left's hatred of him was implacable, I've read that was true since around 1948-50. But things weren't quite so bad after he left the scene. We loathed Slick Willie with a passion (now, not so much...), but we could at times work with him.
The 2000 election, though, that really polarized things, protesting the legitimacy of an election at the highest levels is utterly dangerous (one of the greatest things about our sorts of systems is solving the succession problem, one set of people running the nation replacing another), and Obama hasn't helped.