I think Rush senses that Trump may win and since he is a friend of Trump, he just might get another invite the the White house.
I think he also appreciates what Trump should have been teaching the GOPe, but they're so thick they don't get it.
I do think he would support Trump if he won, which is likely right now. Unlike some of the crazy Cruzerorloser voters (Cruzistheonlyoneandagod), Rush isn't going to totally throw Trump under the bus for his mistake of using leftist talking points to help destroy Jeb.