The simplistic reporting done by much of the mainstream media is leading some to the impression that Trump will probably reach the 1,237 needed to lock up the nomination in the first ballot. However, despite 'leading' in Arizona, Pennsylvania and California, he will likely lose all three.
Arizona and Utah will hold their primaries on March 22. The recent polls for Arizona average the following:
Cruz 21.0 %
Trump is a 'love him or hate him' candidate. One would assume that very few people who are still undecided are likely to break for him. Most of those undecided were probably unsure between Kasich and Rubio and now that Rubio is out, will either vote for Kasich or, despite being 'likely voters', stay home.
Cruz may get a substantial number from people who are waiting to decide which candidate is likely to beat Trump. So, Cruz is the likely winner. He is also the presumptive winner in Utah, which means the delegate count will be close after March 22 between Cruz and Trump.
Wisconsin holds its primary on April 5. There have been no recent polls and, as such, is a critical unknown in the race for 1,237 delegates.
New York holds its primary on April 19 and Trump is the presumptive winner. On April 26 Connecticut, Rhode Island, Delaware, Maryland and Pennsylvania hold their primaries. There have been no recent polls in Connecticut, Rhode Island or Delaware, but one would assume strength for Trump.
Maryland has had one recent poll
With Rubio out, this is too close to call between the three.
Pennsylvania has had two recent polls with the average as follows:
Rubio/Kasich totals are in the lead and with the high undecided, one would expect a Kasich win.
Indiana has its primary on May 3 and there has been virtually no recent polling. One would expect, based upon the polls in similar states that this will be a contest between Cruz and Kasich.
Nebraska and West Virginia have their primaries on May 10.
Nebraska is polling as follows
If the undecided break toward Rubio/Kasich, they would be projected to win the state. However, Cruz has been winning neighboring states and that is a clear possibility. Either way, Cruz and Kasich will average 34.4% if Trump gets no significant undecided, and, therefore, one of them should win.
In West Virginia, Trump is getting 44.0% of the vote and should take the state.
Oregon holds its primary on May 17. There have been no recent polls
Washington hold its primary on May 24. There have been no recent polls.
June 7 is the critical and last primaries, including California, Montana, New Jersey, New Mexico and South Dakota. Only California has been recently polled. However, one would expect New Jersey to go to Trump and Montana, New Mexico and South Dakota to go to Cruz. In California
While Trump currently leads, it seems unlikely that the Rubio vote or the undecided are likely to go to him and Kasich actually looks like he is in the best position.
While the polls still have a significant number of poorly polled states and several of the critical states have very large percent undecideds, the sum total does not suggest that Trump will reach 1,237 on June 7. Also, in the absence of a Cruz/Kasich consolidated ticket, which probably could get a first ballot nomination, it does not appear that the GOP can avoid a contested convention.
As ably described in this New York Times article and argued by Hugh Hewitt, there is a separate battle to select the individuals who will become the delegates who will be bound on the first ballot by their state primaries, but will usually become free to vote as they choose on the second and subsequent ballots. Trump's problem is that this process takes place at the State convention and long time party faithful delegates select party faithful National delegates.
While, generally, Trump's delegates will be bound to him for one vote but are not likely to have significant loyalty to him in subsequent ballots. In other words, once the first ballot selects no winner, Trump will be hard pressed to keep the delegates that he has. They will tend to flood to Cruz and, if he is still a candidate, Kasich.
There are two ways that candidates and party leadership can influence the voting in subsequent ballots. They can talk a candidate into withdrawing. Unlike the 1952 Democratic convention, they only need to talk one into withdrawing, since it then is a two man race and someone will have the majority of delegates. That definitely won't be Trump and the GOP leadership has more leverage on Cruz. So that is a possibility.