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.