FiveThirtyEight has a discussion post on the possibility of the Republicans going into their presidential nominating convention with the nomination still undecided: what's the likelihood and what might happen.
As I read it I thought fondly of the good old days, when states had favorite sons controlling blocks of votes who could wheel and deal in the famous smoke-filled rooms to agree on a nominee. That's how we got President Lincoln, wheeling and dealing. They added so much to the drama of the convention as compared to these days, when primaries and caucuses have allocated the delegates to the candidates.
From the post it seems there will be mass confusion if the balloting goes to a second round--delegates will be released from their pledges but there will be a lack of people who can make deals. We'll see if a Rand Paul who may have a bunch of KY delegates is able to deliver them to a Rubio, or a Cruz is able to steer his delegates to a Kasich (in return for a Supreme Court nomination?).