I suppose this is largely a matter of definitional nuance, but I find Ezra Klein's principal assessment of Paul Ryan to be ingratiatingly generous and pathetically Beltwayean:
[H]e’s smart. This shouldn’t need to be said, but some liberals seem to think Ryan’s intelligence is some kind of facade. In this view, he’s really a robotic Randian who does little more than spout talking points.
Ryan may be smart. I don't know. But I do know that Klein's applied measurement of intelligence--that "He’s sufficiently engaged in the policy conversation that he knows both the arguments for and the arguments against his positions"--is no real measurement at all. Shifty used-car salesmen are abundantly practiced in the art of anticipating objections; they know every one of them and they can seemingly pulverize every one of them, but that's scarcely a sign of raw intelligence.
The used-care salesman, like Ryan, is only one species of the single-minded ideologue. His cerebral universe consists of selling that car. You may not need the car, and in fact buying the car may be the dumbest thing you could possibly do at that moment. However the vigorously ideological salesman will hurl memorized, fabricated reason after memorized, fabricated reason why you should indeed buy the wretched thing, and, assuming you're weak-minded enough and insufficiently self-interested, he'll wear you down.
Before you know it you're bumping along in a cataclysmic wreck of a lemon wondering, Why the hell didn't I stay with what I had?
And your principal, one-word assessment of that slithering salesman probably won't be, Wow, he was smart.