This is difficult.
I can easily imagine that Kennedy would have come relatively close had he lived. Daley's support was not inevitable-but given Daley's history with Johnson, his lukewarm attitude towards Humphrey, and his relationship with the Kennedy family, I can see Daley throwing his weight behind Kennedy-and perhaps he persuades some other bosses to do the same.
But in terms of delegates-that's not enough.
I'm not sure there's a way to overcome Humphrey's delegate lead.
Perhaps the task is easier if there's only one anti-Humphrey candidate in the race. Said candidate would almost have to be Kennedy given McCarthy's lack of the sort of institutional resources needed to win.
Daley's support isn't guaranteed-but it's a prerequisite for anyone but Johnson or Humphrey to be nominated. Daley would never support McCarthy but he might have supported Kennedy.
Kennedy considered running for a long time-but only entered the race after New Hampshire.
Let's say Kennedy enters the race earlier-McCarthy makes waves about wanting to run-but his nascent campaign goes nowhere.
Kennedy-not McCarthy-is the candidate who challenges Lyndon Johnson in New Hampshire and comes close to defeating him.
Johnson given his historical antipathy towards Kennedy is afraid of creating a perception that Bobby Kennedy has pushed him aside. He therefore decides to stay in the race however reluctantly.
In the primaries Kennedy mostly runs unopposed-while Johnson determined not to be footnote to two Kennedy administrations tries to secure boss support.
But Johnson's hold on Mayor Daley in Chicago is tenuous. Johnson had always had a weaker relationship with Daley than the Kennedys' had. After the primaries-Daley throws his weight behind Kennedy.
Several other bosses who had in private promised to support Johnson's renomination begin to have second thoughts after Daley makes his decision. Worried that Johnson cannot win while Kennedy might-more bosses begin to leave Johnson's camp.
In the midst of what looks like his worst nightmare come true-Johnson has a minor heart attack. He is informed by his Doctors that a continued campaign for reelection will kill him.
Johnson removes himself from contention. Johnson has left the race for the nomination too late to develop the infrastructure for a Humphrey nomination. Senator Robert Kennedy of New York wins the Democratic nomination.