Rush is a Free Traitor™. Yeah I said it. Thank me.
That's the end result. I think Rush developed his own ideas in most areas, but I also think he had no real beliefs concerning trade and he eventually just adopted positions from some of the think tanks.
When I started listing to him in 1991, NAFTA and Perot's positions soon became hot topics. For weeks Rush sort of thought aloud about NAFTA, never coming out for or against it. I though he might oppose it, but finally he came on the air and seemed to just read a pro-NAFTA position paper and that became his position.
He's just followed the GOPe on trade and some other issues since then.