Humphrey didnt even run in the prymaries in 1968.
If Humphrey didn't run in the 1968 primaries then how did he become the Democratic nominee?
Back then superdelgates were the majority of all delegates, and thus theoretically a candidate didn't have to run in the primaries if many superdelegates supported his bid for the nomination.
So screw the voters of our party. After all we're politicians and we know more than you? That's a great way to advocate democracy and freedom. So much for the popular vote.
That's literally exactly what happened (Though Humphrey did run in some of the later primaries). Had R. Kennedy not gotten shot, though, he very well could've garnered enough Establishment support to beat Humphrey at the convention. Eugene McCarthy, who was, frankly, pretty s&&tty a the electioneering side of politics, was never going to upset the Establishment at the Convention.
Daley's cops beating the hell out of kids outside the Convention was horrendous from a PR standpoint and really undermined the Democratic Party for years.
I'm pretty sure Humphrey didn't run in any of them. The DC primary in 1960 was the only contested primary he ever won.