Nate Silver and his crew over at fivethirtyeight.com discuss the possibilty of a brokered Republican convention, meaning that no candidate has a winning number of delegates by the time the party convenes in Cleveland and they fight it out there. That would be enormously entertaining. So would the scenario where Trump storms out of the G.O.P. and makes a third-party run. I don't see either of these things happening.
Once upon a time, political conventions weren't coronations and infomercials. Unless there was an incumbent up — and even occasionally when there was — everyone showed up with some delegates but not enough. There were plenty of delegates who were unpledged to a candidate or were pledged to a "favorite son" candidate so, at the opportune moment, they could shift their votes to a real candidate and give him enough to win. Then, once the nominee was selected, that person had a matter of hours to settle on (and insufficently vet) a running mate. It was all exciting to watch but I'm not sure it ever served the party or the country.