President Trump promised again on Tuesday night that Republicans would repeal and replace Obamacare. It was good to hear this expression of resolve, for achieving the desirable goal will require persistence and follow through.

Trump has been consistent in calling for repeal and replace, as he has on other policies such as trade protectionism and a border wall. But his debating and other rhetoric does not evince purposeful, clear, step-by-step thinking. So turning the huge policy goal into legislative reality is likely to present a challenge to the president orders of magnitude greater than he yet realizes.