Robert F. Kennedy's assassination probably robbed the United States of a second Kennedy president as well as the disgraceful final years of the Richard Nixon Administration that culminated in the Watergate scandal. Kennedy'a death allowed Vice President Hubert Humphrey to gain the Democratic nomination--one that he almost certainly would not have won had Kennedy still been alive. Kennedy, who entered the race late, was garnering support from anti-war activists as well as followers of his incredibly popular brother, the late John F. Kennedy. RFK would have likely won the Presidential election: He was far more popular than Humphrey, who was irrevocably linked to the unpopular President Lyndon B. Johnson; yet Humphrey made it a close race against Nixon and third-party candidate George Wallace. Though much of Kennedy's support would have come from admirers of his brother, Kennedy's run would have only gained more momentum had he survived. Kennedy would have likely chosen former Georgia Governor Carl Sanders as his running mate, which would have probably reversed Wallace's win in that state--and probably given Kennedy other Southern states won by Nixon. Several projections comparing a Kennedy-Nixon-Wallace race gave Kennedy the victory.
The assassination of Robert F. Kennedy by Sirhan Sirhan on June 6, 1968 helped to allow Richard Nixon to win the general election more easily than he would otherwise have. It is likely that RFK would have won the Democratic nomination had he not been killed. He would have done better against Nixon than Hubert Humphrey did.
Hubert Humphrey had one big flaw. He was Lyndon Johnson's vice president. Johnson's conduct of the Vietnam War was so unpopular that Johnson declined to run for a second term. Humphrey was, of course, tainted by his connection to Johnson and his policies. If Kennedy had not died, he would have been able to run as an anti-war Democrat with no connection to LBJ's failure. (And that might have spared the party the spectacle of the violence at the convention in Chicago.) This, when added to his charisma (which Humphrey also lacked), would have made him a more formidable opponent for Nixon. Instead, Nixon won the electoral vote rather easily.