Something extraordinary is set to happen on Thursday: The Supreme Court will interpret part of the Constitution for the first time. Neither the justices nor any of their predecessors have ever heard a case about the Disqualification Clause, a post-Civil War provision in the Fourteenth Amendment that bars participants in “insurrection or rebellion” from holding political office. The court is stepping out into freshly fallen snow.The stakes in Trump v. Anderson could not be higher. In December, Co