Most everyone following the United States 2016 election has heard about Donald Trump's rise to power in the Republican Party. As of current, he has the most delegates, and is on track to win many more. My question is this: if Trump wins the majority of the delegates, is he locked into the nomination? Can the GOP committee independently choose another candidate to be the nominee, even if Trump has the majority of delegates?
Officially, no. Practically, yes. Feasibly, maybe.
Officially, all delegates chosen to go to the national convention are bound to vote as their state allocated them, but only on the first ballot (or occasionally the first few). Additionally, as of this election cycle, the Republican equivalent to the Democratic superdelegates (3 per state) are bound to vote as their state did. So officially, if Trump wins the majority of delegates beforehand (1237), he will be chosen as the nominee.
That said, the rules governing the nomination process are decided solely by the Republican party (as a private organization), and can be changed at the convention itself. This article discusses the sole example from the past:
The 1980 Democratic convention in New York (pitting incumbent President Jimmy Carter against the-dream-shall-never-die candidacy of Ted Kennedy) may provide the most relevant model for anti-Trump Republicans.
Like the Republicans today, Democratic delegates in New York were bound to their candidate for the first ballot. But badly trailing in the delegates, even as Carter’s approval rate hit 21 percent in the Gallup Poll, the Kennedy backers came up with a last-ditch strategy.
Their clever idea was to free the delegates to vote their conscience instead of being robots forced to obey the results of the primaries or caucuses that selected them. Overturning the Robot Rule would have been possible, in theory, because conventions as a body have the power to change the rules — and delegates are always free agents on procedural votes.
It also points out:
It is worth remembering that — even with a delegate lead or a majority — Trump would face built-in disadvantages in Cleveland. Paul Ryan would be the convention chair and other GOP insiders would probably control relevant committees like convention rules and party platform. In some states, Trump does not get to pick his delegates slates, but instead is saddled with party stalwarts of dubious loyalty.
Thus, it is very possible that even with a majority of delegates pledged to him, the Party will act to deny Trump the nomination.
Finally, there's the question of whether the Party would do that. FiveThirtyEight discusses it in the context of "mandates".
But the possibility of a contested convention is part of why the notion of a “mandate” is important. If (for instance) Trump has won 37 of 50 states and 49.9 percent of delegates going into the convention, then technically Republicans might be able to deny him the nomination. For that matter, technically they’d be able to deny Trump the nomination even if he had a delegate majority by changing the rules at the last minute. But the cure might be worse than the disease. It could look as though Republican elites were overriding their voters’ popular will (because, uh, that’s pretty much what they’d be doing). ...
By contrast, if Trump didn’t have that seeming mandate — if he were far short of a delegate majority, if he were still unable to secure more than 34 percent of the vote as we got deeper into the calendar, if he’d started to lose quite a few major states (even if not always to the same opponent) in April and beyond — it would be less risky to deny him the nomination.
So it's only feasible to try and block him at the convention itself if he's not already winning. Otherwise, they risk reinforcing the "elite vs voter" mentality that Trump is tapping into and possibly tearing the party apart.
All that said, if the first ballot fails to select a candidate, which has not happened since the modern primary system started in 1972, then everything is up for grabs. Anyone at all can be nominated, regardless of whether they were actually running previously. They just need to win a majority of at least eight state's delegates on any given ballot. Or the party delegates could decide on any other method of choosing a candidate, including holding yet another round of primary elections (as impractical as that would be). Really, in the case of a contested convention, anything could happen.