The possible release of Sirhan Sirhan has prompted a bit of discussion of Robert F. Kennedy's role in American history, and his prospects.
Early on I was torn between Hubert Humphrey and JFK. Humphrey was the stalwart liberal, the speaker on the floor of the 1948 convention, the Senator leading liberals in the 1950's. JFK had charisma and seemed more popular. Defeating Nixon was important, and difficult; less important and less difficult than defeating what's his face last year, so after West Virginia primary showed JFK could win Protestants I accepted his candidacy.
Robert was the kid brother, feisty. (Interestingly, I find in my memory I had conflated Ted and RFK's college records, to the discredit of RFK.) His reputation among liberals was marred by his work first with Joe McCarthy and then investigating labor corruption with Sen. McClellan. It probably hit a low point when his brother named him attorney general.
Bobby's reputation rose during the 1960's, first with civil rights and then on Vietnam, reaching its peak with me with his speech when MLK was killed.
I'm not sure whether I would have supported RFK or HHH finally. Humphrey didn't fare well as LBJ's Veep. It likely would have come down to the man who ran best against Nixon. We know HHH lost, barely. I think it's likely that RFK wouldn't have been able to unite the party; LBJ would have borne his grudges too long for that.
So, my bottom line is I don't think American history changed because of Sirhan Sirhan. It would have been different, but Nixon would have won, the divisions in the Democratic party would have been there, perhaps even deeper than they were. And Nixon would have continued to be paranoid against whichever Democrat seemed strongest in the lead up to the 1972.