Consider the following three statements:
(1) “I’m arranging the magnets on my fridge to say ‘Cruz’ because he can beat Hillary in the general election.”
(2) “Instead of picking a listed candidate, I’m writing in the phrase ‘the choice of the majority’ for the primary, because it would be hilarious if 51% of the other voters did that too.”
(3) “I’m voting for Cruz in the primary because he can beat Hillary.”
I have never heard anyone say (1) or (2), but there are people saying (3). I submit that if you think through why (1) and (2) are nonsensical, you will see why (3) is also.