Robert Lighthizer wants Canada to know he can pass a revised Nafta trade deal with Mexico whether or not the Canadians join, or so the U.S. Trade Rep claimed Monday. The question is whether this is a bluff, or if Mr. Lighthizer has some special political insight that no one else has.

Our guess is the former because he’d be taking some large political risks to send Congress a new trade deal with only Mexico. Mr. Lighthizer has been assuring President Trump that he has the political skids greased with the help of Big Labor,...