There’s a fair amount of speculation these days about whom Trump will choose as a running mate. Guessing games can often attract a crowd. The names of Ron DeSantis and Marco Rubio, along with even Donald Trump, Jr., are being bandied about. There is a catch. It’s called the Twelfth Amendment: “The Electors shall meet in their respective states, and vote by ballot for President and Vice President, one of whom, at least, shall not be an inhabitant of the same state with themselves.” This particular clause did not change the Constitution. It was carried forward from Article II, Section...