I actually think the support for everybody else is soft and flexible.

Is it possible that some that are caucusing may realize once they are there voting, the only way they can defeat Trump is to move to Paul.
Here is why, Trump supporters aren't moving we know that, it's emotional for them, Paul voters aren't moving they are voting on principle.
The rest are doing it just because, if all those were to move away from there soft support on caucus night once they see the enthusiasm for Paul and little for the other guys, he could come second or actually win.

Or are Americans super stubborn and going to vote for Bush/Cruz/Rubio even if they hate Trump and think there guy can't win either ?