You are probably right.
But this is the primary...heck, it's the pre-pre-primary season, and if we can't vote our convictions in the primaries, when can we??
Winning is always important. One Republican will win the nomination. If your first choice is almost certainly not going to be the one to win the nomination, then it might make sense for you to at some point switch to your second (or third, etc.) choice in order to avoid some even lower preference winning the nomination. That is all. The Republican Party is a coalition and it takes a broad reach to win the Presidency. Certainly Ronald Reagan understood this.