As apparent when a challenge to threaten both parties is perceived, both parties (sitting president Obama overtly and the RNC covertly) coordinate response and act in harmony against the outsider (Trump). Any challenge from within a party (Chris McDaniel) results in voting reinforcements from the opposite camp supporting the incumbent (Thad Cochran).
Unless you have references from party members in good standing, to join the exclusive club within the party which apportions influential positions, to attain postings with the scope to change party dogma, remains a reformation pipe dream. You only fit their mold if you are a good company man.
This is exactly trump should have run third party from the start.