You’re comparing Trump to McCain and Romney ? Lol!
But I do want to make something clear. In 2008, Rush was vehement that Romney met the three legs of conservatism test. In '12, he swore up and down he didn't. IMHO, Romney ran more to the right in '12 than he did in during the primaries of '08. I can't recall any positions that he softened. The litmus test moved further to the right during the intervening 4 years.
So just because Trump will be the standard bearer, don't believe that Limbuagh will give his stamp of approval.