Since his assassination, RFK has become something of a blank slate upon which liberals/progressives of the baby-boomer generation project their dreams of a post-1968 golden age without a President Nixon, Watergate, a President Carter, a President Reagan, etc.
But RFK was a real human being, with a record as U.S. Attorney General and as a U.S. Senator. Prior to 1964, RFK was not all that liberal. He was a centrist Democrat like JFK in the early 1960s, and even somewhat of a conservative Democrat like their father before that time. From 1964 to 1968, his political movement to the Left and his genuine concern for, and outreach to, racial minorities and the poor was not necessarily a political plus.
As JFK's campaign manager in 1960 and as Attorney General, RFK made significant enemies inside the Democratic Party. He occasionally made political mistakes.
The odds were against his winning the 1968 nomination. On the night of June 4, 1968, after he won the California and South Dakota primaries, RFK estimated his own changes of winning the nomination at no better than 50-50%. After those wins, the estimated delegate totals were: Vice-President Hubert Humphrey 561; RFK 393; Senator Eugene McCarthy 258. Out of a total 2607 delegate votes, it took at least 1304 delegate votes to win the 1968 Democratic nomination.