My Ethics and Public Policy Center colleague James Capretta, one of Washington’s great health care mavens, had an extremely useful and important primer on the trouble with Obama’s health care plan on the homepage yesterday. The piece makes use of some newly published data with which the Obama campaign couldn’t have been happy. He really gets at the key conceit of the current Democratic health care agenda: the notion that their plans build on the existing private insurance system. Alas, no.