Angus King is the anti-partisan, independent United States Senator from the cranky Yankee state of Maine. He is giving us a conversational civics lesson in the tradition of James Madison and also of Schoolhouse Rock, the kids’ TV explainer.

James Madison.

Senator King has been in the thick of the frenzy in Donald Trump’s Washington, with a certain distinction. His tone on the Senate floor has been measured, his language old-fashioned, and his message a deadly warning. It’s the Constitution itself that’s at risk. What’s at stake, he has been saying, is the famously balanced U.S. Constitution, “this clumsy system” of self-rule, he calls it, that is “the mainspring of our freedom.” And it is under direct assault as never before in these first weeks of a new presidency. Rescuing that “we the people” charter will mark our place in history, Angus King is telling us. Losing it would mark the end of the American experiment.