It started with the Gary Hart scandal. Guy was cheating on his wife, which had no impact on his ability to govern, he was stalked by reporters in order to break the irrelevant but salacious story and sell newspapers. Ended his career for all intents and purposes. And in the process created a media environment where actual effective handling of the job of governing takes a back seat to pandering to the constituency's emotions while trying to paint the opponent as unfit for office because his dog got its shots a week late. All the Truth is Out, The Republican Noise Machine and Shock Doctrine paint a pretty nihilistic portrait of media and politics at the present if you want to read them and draw connections between three different books that are loosely related by topic.
Technically, it started with Whitewater. Gary Hart was business-as-usual electioneering; slander in elections goes back to Andrew Jackson or before. However, the use of off-topic attacks against a sitting president is straight from Turdblossom by way of Richard Mellon Scaife.
You're right but I was pointing towards a confluence of bullshit in the last 30 years or so. Hart shifted media focus in a destructive way that replaces issues with personal lives. Gary Hart to Whitewater to Monica to secret Muslim, Acorn and Benghazi. I really can't remember a time when political journalism wasn't a joke but I'm only 32 so I don't know that it was ever good in America
And that's why I was specific: You see hand-wavey stuff that happened about the time you were born, while I can point to specifics. Gary Hart was business as usual. Whitewater was the first time an attempt was made to smear a sitting president with the fact that they'd lost money as the victims of a crooked land deal 20 years previously that the perpetrator was already in jail for.