The GOP isn't in control. Each state sets its own rules for elections and have a primary or caucus. Voters decide the nominee. This should be an open letter to conservatives to vote.
Most public figures don't want to push a candidate during primaries because it makes them look weak when their candidate loses.
The problem with certain public figures taking that position this time around is that they've been screaming and beating their proverbial chests about how much danger the country is in and how we're not going to recover if we allow big-government socialism to gain anymore ground.
If we're really in that much danger, and I suspect we are, then they have an obligation to stand up against socialism ... whether it comes from the left or the right.