It is now a familiar pattern — the scandal of sanity. Rick Perry is criticized for supporting discounted higher education for the children of undocumented workers, as though the ignorance of the innocent is an obviously superior policy option. Herman Cain is attacked for supporting a TARP bailout that prevented a national panic. “Owning a part of the major banks in America is not a bad thing,” wrote Cain in 2008. “We could make a profit while solving a problem.” Which is precisely what happened. For all its (considerable) flaws, Mitt Romney’s Massachusetts health reform was based on ideas that originated in conservative think tanks…

Some of this is just the nature of primaries, in which audiences applaud for purity. But there are other factors. Over the past few decades, the GOP has become a more conservative party. The development of self-consciously conservative media — on radio, cable and the Internet — has provided a welcome alternative to the bias of the mainstream media. It has also simplified many public debates into a contest of ideological teams — a tendency shared by self-consciously liberal media. Candidates, pundits and voters are called to join one side or the other, doing nothing that will give comfort to the enemy. But ideological conformity easily becomes cultural isolation — the development of assumptions, language and views disconnected from the broad middle of American life…

And this approach makes for bad politics. There is a reason that the purest candidates are often not the strongest candidates. Appealing, successful politicians have usually built unexpected governing coalitions, engaged in creative ideological outreach and shown intellectual independence.