Even the wingiest of wingnuts understands that you can't keep cutting taxes forever, and after 2003 the tax cut jihad simply ran out of steam. There were no more taxes to cut. On the culture war side, as the Pew charts confirm, the problem is that America is getting slowly more culturally liberal as time goes by. Partly this is a generational thing and partly it's just a continuation of the same slow march of social tolerance that's been a hallmark of the past half century. Every year there's one or two percent more of the country that doesn't hate gays, doesn't want to ban abortion, and would just as soon see the Ten Commandments stay in church.
In other words, the Republican party may yet be forced to become a party of principle.