Partisan about-faces are inevitable, but they’re arguably easier on constitutional matters. Change your mind on immigration, and your constituents may well revolt. Change your mind on whether a president has the power to do things on immigration policy that your constituents already support, though, and only your partisan critics and the occasional law professor will care.

This is why it’s so remarkable that our constitutional order has lasted so long, given the perpetual incentive — common to both parties, and all three branches of government — to abandon its safeguards in order to push a particular agenda.

Today those incentives are strongest for Democrats — visible in their support for Obama’s more dubiously constitutional forays, and also in the widespread liberal attempt to explain his struggles by casting him as a Gulliver tied down by an antiquated system of government.