How Donald Trump Becomes the GOP Nominee: The Path to 1,237 Delegates

— -- While the Republican field has now been cleared for Donald Trump, the road ahead is still messy for the front-runner to become the official nominee at the Republican National Convention in Cleveland, in July.

Currently, Trump has 1,012 bound delegates, plus an additional 43 unbound delegates who are free agents -- though they have told ABC News they support Trump.

Most likely, Trump will hit and far surpass the needed 1,237 in total delegates on June 7, when delegate-rich states like New Jersey and California cast their ballots. He is predicted to take most of the 228 delegates up for grabs on that day.

Before June 7, though it is mathematically impossible for Trump to clinch the nomination with only bound delegates, he could still hit the winning delegate number with unbound (free agent) delegates after the primaries in Oregon and Washington, which happen in late May.

To do this, he will need to win by wide margins in West Virginia, Oregon and Washington. He will also need to take winner-take-all Nebraska and earn the allegiance of nearly all of the currently uncommitted, unbound delegates and those who currently back Ted Cruz.

Heading into Cleveland, Trump will likely pick up some of the 545 delegates currently pledged to Ted Cruz and 153 pledged to John Kasich.

The GOP leaves it up to the state Republican parties to determine how these delegates are allocated after candidates drop out. In many states, delegates become unbound, sometimes only after the candidate withdraws in writing. In other states, delegates remain locked in even when the candidate leaves the race. In a small number of states, the state party will reallocate the delegates to a remaining candidate, according to election expert Josh Putnam.

As Cruz and Kasich delegates become free agents, there is likely to be unity around Trump, said a GOP insider. “We will see pockets of resistance, but generally what we have seen historically is the party apparatus falls into place behind the presumptive nominee.”

At the polls, low voter turnout and disproportionate numbers of Trump supporters are expected, said Putnam, even though Cruz and Kasich’s names will remain on most ballots. “Once the last viable challenger has dropped out, voters are less inclined to come out when their vote won’t be meaningful and decisive.”

While the possibility of a contested convention is essentially off the table, the Republican National Convention could still get heated. “It will still have its Cruz sympathizers and Party regulars who may try to reign in Trump,” said a GOP insider, “but the motivation will be to line up behind him.”