The presidential nominee quoted Franklin D. Roosevelt and Thomas Paine, the most radical of the Founding Fathers. He asked all Americans for their support. “More than anything else,” he said, “I want my candidacy to unify our country; to renew the American spirit and sense of purpose. I want to carry our message to every American, regardless of party affiliation, who is a member of this community of shared values.”

This was Ronald Reagan, accepting the nomination of the Republican Party on July 17, 1980, at Joe Louis Arena in Detroit with a speech that in tone and much of the substance was the...