Democratic Rep. Adam Schiff isn’t a constitutional scholar, but he plays one on Impeachment TV. His latest gambit is an attempt to redefine “bribery” in the Constitution to include President Trump’s behavior toward Ukraine.

The Constitution specifically mentions bribery, along with treason and high crimes and misdemeanors, as impeachable offenses. It offers a definition only for treason. In an interview with NPR on Nov. 12, Mr. Schiff opined on Mr. Trump’s impeachable offenses: “Well, bribery, first of all, as the Founders understood bribery, it was not as we understand it in law today. It was much broader. It connoted the breach of the public trust in a way where you’re offering official acts for some personal or political reason, not in the nation’s interest.”

We didn’t realize Mr. Schiff was a constitutional “originalist,” but note his legal sleight-of-hand. Mr. Schiff is not accusing Mr. Trump of bribery based on a current statute. He’s trying to broaden its meaning to fit his current impeachment purposes—supposedly with a James Madison stamp of approval.

He’s wrong about the law and constitutional history. The Founders understood bribery then, as we do now, as involving the offer or acceptance of a quid pro quo. A friend of ours who knows this history supplied us with details from the period.

William Blackstone, the preeminent English law expert of the day widely admired by the Founders, wrote that bribery “is when a judge, or other person concerned in the administration of justice, takes any undue reward to influence his behavior in his office.”