This ought to be a locked-in-concrete, dead-certain Republican year. America has a two party system, and Americans have an instinctive habit of giving both sides a turn at the presidency. Unless the incumbent walks on water like Ronald Reagan, after 8 years, the American public is hankering for a change and typically turns the ball over to the other team.
Beyond that, running against Hillary is a lot like running against the mean old woman of every Blues song, who moreover seems likely any day to be indicted.
But, along comes Trumplestiltskin.
In Scenario 1, Trump wins nearly all the rest of the primaries. The GOP caves and gives him the rest of the votes he needs for the nomination, and then the Party splits. Movement conservatives, the people who nominated Barry Goldwater and elected Ronald Reagan, and the intellectuals (very possibly including the Neocons), conceivably including socially-moderate, but snobbish, Country Club Republicans take a hike. In significant sectors of the Party, voting for The Donald is just infra dig, and some contend that even Hillary would make a more responsible first magistrate. Trump loses, Hillary becomes President.
Scenario 2, Trump has a ceiling, getting a plurality of delegates on the first ballot, but no majority. Conservatives and GOP Establishmentarians will die in the last ditch before nominating Donald. The knives come out. Trump delegates are pulled away on subsequent ballots, and a brokered convention nominates Cruz or Rubio. Donald J. Trump is no sportsman. He immediately forms a Third Party, and in the election proceeds to pull all the numbskulls and Reagan democrats away from the GOP candidate. Hillary becomes President.
There is no scenario 3.
The Trumpkins are going to say: This isn’t fair. We’re having a Revolution, and the rest of you are supposed to get on board. Donald Trump is our only hope of Change. Change you can believe in. And the rest of us, the sane people, are going to make little circle next to our temples with our index fingers at the idea of turning all the power of the Presidency over to a totally-unprincipled, egomanaical airhead with the morals and manners of the most spoiled rich kid in the entire country. Some of us actually know what happened when they made Gaius Julius Caesar Augustus Germanicus, nicknamed “Caligula” (“Little Boots”) by the Army, Emperor. It was not pretty.