Cruz is the only one what? I don’t understand your reply unless you mean Southern Baptist. Walker is also the son of a SB pastor, and Huckabee is also SB. Trump is Presbyterian.
I could give a sheet about their religious status. (unless they are muslim... and that pretty much instantly disqualifies them from everything in my mind)
Cruz is an ardent defender of the constitution as constructed, which by default makes him a limited government conservative.