Donald Trump had a complete meltdown Thursday night when he got locked in this exchange with Marco Rubio over health care. Rubio kept pressing him on what his plan for health care was, and Trump responded by incoherently talking about getting rid of “the lines around the states.” Essentially, Trump wants to increase competition by allowing insurers to sell plans across state lines without regard to the states’s own insurance regulations.

Setting aside the fact that Trump’s understanding of health care policy is woefully inadequate, his one idea on health care isn’t even a good one. Granted, this is an idea a lot of Republicans have floated and, in theory, increased insurance competition is needed and state insurance regulations are often an impediment to this. But in practice, the idea runs into the buzzsaw of federalism.