I think the tipping point was '92. Back then, a presidential candidate's history of illegal drug usage was a big deal, and should have been a deal breaker.
When Clinton addressed the nation to say, "I smoked, but didn't inhale," I was personally insulted that a candidate would tell such a ridiculous lie. I thought, "He must think the electorate is a bunch of idiots." That November, he was proved to be right.
That is where I have marked it also.
Family and friends are sick of hearing it, but 1992 was when USA became a nation of reprobates