“We don’t know where Long would have ended up,” Brewer says. “Certainly, the assassin’s bullet stopped him short of where he wanted to go.” Long was an aggressive and popular proponent of progressive ideas still less than halfway through his first term in the Senate; he could have pushed the Democratic Party further left, if he hadn’t made too many enemies along the way. As Sokolsky wrote, “Huey Long never could have been elected President of the United States, but he forced one President to adopt an absurd fiscal program, and succeeded in balancing the political scale so accurately that he was, after Franklin D. Roosevelt, the most significant political personality of his day.”

But he was also a staunch isolationist and an autocratic hoarder of power. As first World War II and later the Cold War and the civil-rights movement came to dominate American politics, the country’s populism grew more reactionary and nationalist. Gerald L. K. Smith, the man who co-founded the Share Our Wealth Party with Long, went on to lead the isolationist, racist, anti-Semitic, and anti-immigrant America First Party. Long’s abrupt and early death makes it unclear what path he would have taken, or what his aggressive brand of progressive politics would have looked like given more federal power, and more time.

If left-wing populism continues to gain traction within the Democratic Party, it could become more clear what that power would look like—with or without Long’s particular edge of authoritarianism.