A decade ago, Donald Trump descended the golden escalator at Trump Tower in New York City and ignited a political movement that has reshaped American politics. In a memorable turn of phrase, Trump promised supporters of his 2016 presidential campaign that “we are going to make our country great again.” Since then, the Make America Great Again movement has dominated the U.S. political conversation, reshaped the Republican Party and become a lucrative brand adorning hats, T-shirts and bumper stickers. When asked what MAGA means to him, Trump, in a 2017 interview with The Washington Post said, “To me, it meant...