Of course, it is impossible to know for sure what would have happened in the 1968 election had neither of these two men been killed. King was assassinated in April and Kennedy in June. Many things could have happened between those dates and the election that would have changed the outcome. However, we can certainly speculate that the killings helped Richard Nixon to win the election. There are two ways in which they might have done so.
First, the killing of Kennedy removed a man who looked like he might be the strongest Democratic candidate. Of course, much could have happened in the remainder of the primary season, and many historians do not believe Kennedy would have won the nomination. However, we can at least speculate the Kennedy’s death removed a candidate who could have been more of an obstacle to Nixon than Hubert Humphrey was.
Second, the killing of King helped to make a case for Nixon’s law and order agenda. Nixon was running in part on a strategy of appealing to white conservatives who were appalled by the counterculture and by the violence that erupted in black communities during the “long hot summers” of the 1960s. King’s assassination sparked more riots and these riots helped to solidify the perception among many white conservatives that Nixon-style law and order policies were necessary to save the country from chaos.
Again, we cannot know what would have happened, and we cannot know for sure what effect these killings had. But we can speculate that they helped to make it easier for Richard Nixon to win the 1968 presidential election.