You realize he does not set policy? I'm guessing you don't.
He certainly does, indirectly!
He can have a lot of input into party rulemaking which can ultimately influence policy by favoring one candidate over another. But I don't believe Martinez will abuse his position with blatant favoritism, at least until one candidate acquires a lock on the nomination.
It's apparent that a lot of folks don't really understand the inner workings of how a national political party operates. The real power centers are in obscure places like the Executive Committee of the party's national committee, and the Platform Committee at the convention, which is mostly controlled by the presidential nominee.