History repeating itself? RFK ran in the 1968 election against a failing incumbent Dem president who had gotten the US involved in a senseless war. And a republican won that election!
Actually, LBJ didn't run in 1968 so it was an open primary.
I don't see RFK Jr as viable in the Dem primaries. Unless someone like California or Michigan's governors jump in, I don't see any real threat to Biden being nominated.