Are betting markets more accurate than polls? What kind of chaos would a second Trump term bring? And is U.S. democracy really in danger, or just “sputtering on”? (Part two of a two-part series.)

Sure, we all pay lip service to the Madisonian system of checks and balances. But presidents have been steadily expanding the reach of the job. With an election around the corner, we updated our 2016 conversation with the legal scholar Eric Posner — who has some good news and some not-so-good...