But if the primaries and caucuses produce no consensus candidate, then it is perfectly legitimate for the delegates to exercise their sovereign authority. In fact, it is essential for them to do so. Since the first party nominations— dating all the way back to the congressional caucuses in the Jeffersonian era— the mandate has been for a candidate to win a majority of the participants before he becomes the nominee, and for good reason. A party nominee is not running just as an individual, but as the representative of a coalition. If a majority of caucus members, delegates, or voters have selected somebody else, how can that nominee be said to be representative of the whole? This is the one constant amidst all the changes in the presidential nominating process from 1796 through 2016: The nominee must represent the whole party.
And it is in this way that the convention is not simply an appendix. Today, it serves a function similar to the House of Representatives whenever no presidential candidate receives an Electoral College majority: The House selects from the top three finishers, with the winner being the candidate who receives a majority of votes from the state delegations. The logic behind this rule is that the president is the government officer who represents the whole country, and if a majority of the country — acting through the Electoral College — fails to agree on a candidate, selection devolves to the House, which must continue to vote until a majority coalesces. The House has not been required to serve this function since 1824, as the people have reached agreement on their own. But the procedure is in place as a fail-safe. The same goes for the GOP nominating convention. If the Republican electorate fails to agree amongst itself, the choice devolves to the delegates.