I don't think so. Bobby is viewed so romantically now because he got shot. Like JFK he was his Dad's son and not the best retail Politican. I don't think he could have gotten the nomination at all or even come close to dead locking the convention.
If I remember correctly, in '68 only about 1/3 of delegates were picked by primary. Bobby had pissed off traditional Democrat supporters.The labor Unions (Jimmy Hoffa), the South, the Scoop Jackson types, who the hell knows what Hoover had on him. The Kennedy'' didn't keep their end of the bargain with the Mob when Jack was elected in '60 (and who led the crusade against the Mob as the Attorney General, hmmm?) Plus RFK had royally pissed off the traditional Democrat power brokers, (think Richard Dailey)
I also believe that unlike President In Kennedy that Bobby was clearly a victim of a conspiracy. Someone really wanted him dead. The Ivers-Johnzon .22 fired 8 rounds 13 rounds were fired. Someone was not happy with the idea of him running. It's like Sam Giacanna said when JFK got shot, if you want to kill a dog, you cut the head not the tail.) Well Bobby was going to be the Dog. He also kind of threw Carlos Marcello out of a airplane over Guatamala.
Humphrey was clearly going to get it, if McCarthy hadn't been the leftist darling, LBJ would have been the guy. I still laugh at this: my Mom was a huge McCarthy supporter (she hated Vietnam. I think mainly because her fiance, my Dad was at Hue City.) In the pamphlet she was sent by Humphrey campaign sent her and every other volunteer was basically "cut your hair, dress nicely and knock off the Hippy Shit, when you talk to normal people.)
Now, if RFK had somehow gotten the nomination, Nixon might pick a different VP (think Rockefeller) RFK was a Senator from NY. Rocky had been Governor of NY, although Rocky had the Happy problem, too.
The second thing can you imagine the '68 Chicago convention if RFK was the nominee? Mayor Dailey would have lost it!