A voice from the past has shaken President Donald Trump.

When Ontario’s provincial government ran a 60-second ad attacking protectionism during the World Series last week, President Trump was furious. He suspended trade talks with our northern neighbor. He demanded the ad be pulled. And he announced an additional 10 percent tariff on Canadian imports “over and above what they are paying now.”

Why the outrage? Trump accused Canada of trying to influence the U.S. Supreme Court, which hears arguments next week on the constitutionality of his “Liberation Day” tariffs. But I suspect Trump was less bothered by the ad’s content than by its narrator: President Ronald Reagan, delivering his April 25, 1987 radio address.