Technically unbound, but they are active in local politics and business, It would be prudent for them to vote as promised in the first round of voting. After that, all bets are off.
Trump needs to start courting unbound delegates and even those bound to other candidates. He doesn't have to offer bribes, just be nice, ask about their concerns, and express an interest in their support. If he brings them with their families to one of his resorts for that discussion, that is completely legal and a common practice (and Trump has a huge advantage in that direction!).
If Trump promises support for the issues of most concern to them, that should also help. I believe that Trump can even legally inquire about their interest in working in his administration, so long as he does not directly offer to trade patronage jobs for their votes. It's time for him to play the game by the rules and start winning delegates, including courting the delegates who are bound to him so they will stay loyal.
But it's easier for Trump to go on Twitter and Hannity and whine.
He'll probably do that.
“Trump needs to start courting....”
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This is Trump’s big problem...he has ignored the grassroots schmoozing part of the process until very recently...
Cruz and his folks on the ground have probably been talking to these potential delegates for a year...now Cruz is getting the big $$$ helping him...can buy a lot of Super Bowl LI tickets in Houston next February!