All these references to the mythical "GOP Establishment" are about to drive me nuts. There is one commentator on the air who keeps acting like a multi-ballot convention will be controlled by some mythical ghost finger from the RNC. That's just not the way things work. If a multi-ballot convention picks Cruz, or Kasich, or Rand Paul, it'll not be because of a conspiracy but because that's who the delegates want. Abraham Lincoln was nominated on the third ballot, interestingly, when four Ohio delegates switched their votes late in the roll call. If the person with 48 percent of the vote on the first ballot had been given the nomination, we would have had President William Seward, a good man but not the skilled politician that Abraham Lincoln turned out to be.
Comparing this cycle to that of 1860 is a bit disingenuous. The first primary in the United States was not until 1912 (Oregon, the first to set one up). Read The Bully Pulpit by Doris Kearns Goodwin for more information about that awesome election between Roosevelt and Taft. That got messy, because only 20 states had elections, the voters wanted Roosevelt, but Taft was able to control the party. Thus, he received the nomination as the sitting president. Before that, it truly was the 'Establishment' that chose the nominees of the party, not the voters. Slowly, other states starting getting on board with open caucuses or primaries.
The craziness of the 1968 Democratic National Convention set the current process in motion. Since that year, the top vote-getter from each party has been the nominee. That is the voice of the people, whether many choose to agree with the voice or dissent.
As a fan of the game of politics and presidential elections, I am eager to see how this plays out. However, there is no precedent for somebody who was not on the ballot for the primaries to be selected in an open convention. The great story of 1860 is one of back-door politics, not of the will of the people being overturned.
In 1976, Republicans had an open convention between Gerald Ford and Ronald Reagan. Ford had 1,106 (though some places list it as high as 1,121) delegates, Reagan had 1,034. That was a difference of only 72 delegates, with 119 uncommitted. The winner needed 1,130 to earn the nomination. It was undecided before the convention, but once again, the only two candidates were the two on the ballot and the winner was the one with the most delegates and the most votes.
Point being, the people now vote, not the Establishment. If the Establishment overrides the will of the people, I think the drive to fracture the party in a year when people feel that the government is not acting in the best interest of the people will be high.