This is politically smart because Democrats cannot legitimately charge that Romney is “ending Medicare.” But it is also substantively smart because, while people like me believe that intense competition among private insurers will lead to more innovation and cost reduction, we can’t really be sure. The Romney approach sets up a prudent experiment. If real competition works, seniors will migrate toward that. If it doesn’t, seniors will stay in Medicare and conservatives will have a lot of rethinking to do.

Romney’s plan still has some holes in it (how fast would premium supports grow?), but it exemplifies the sort of big reformist vision that should be at the center of a serious Republican campaign. The U.S. is beset by sclerotic institutions: health care, the tax code and the education system among them. To thrive, these institutions need a burst of creative reinvention. The point, as Levin writes, is not to talk gloom and austerity but to confidently set the stage for an avalanche of innovation.

Romney is running in an atmosphere in which it is extremely difficult to remain serious and substantive. Yet he is doing it. Democrats should not underestimate him.