The characters on The Plot Against America, David Simon’s alternate history series on HBO, are about as surprised to hear that aviator Charles Lindbergh is running for president as we are watching from home. Why would the American “hero” who flew across the Atlantic ocean want to pivot to politics? In reality, he already had. Charles Lindbergh’s America First Committee on The Plot Against America was a very real pro-fascist organization. Thankfully, unlike in the new HBO series and the Philip Roth novel upon which it’s based, the real group was quashed. Its “America First” catchphrase, as those living in the Trump era well know, was not.

Lindbergh is most famous for three things: flying across the ocean, a dance craze called the Lindy Hop, and his son’s kidnapping and murder that became known as “The Crime Of The Century.” But what gets lost in all that are his political beliefs, which The Plot Against America brings to light for a wider audience.

It all stems from his America First Committee, which was founded in 1940 and disbanded by 1941. Originally, this group just aimed to keep Americans out of World War II, but then they started to seem more like they sympathized with the Germans, especially once Lindbergh got involved as their spokesperson. Lindbergh gave dozens of speeches criticizing the Roosevelt administration and calling for an “isolationist” approach to the international conflict. He also turned some of his criticism to Jewish newspapers. (He’s not the only famous person to be associated with the AFC, by the way. Other contributors include Gerald Ford, Lillian Gish, Frank Lloyd Wright, and John F. Kennedy.)

Lindberg denied being anti-Semitic, but Nazis in Germany praised his efforts to essentially convince Americans that Jewish Germans didn’t need American intervention. He was also quoted in a 1939 issue of Reader’s Digest saying this:

“We can have peace and security only so long as we band together to preserve that most priceless possession, our inheritance of European blood, only so long as we guard ourselves against attack by foreign armies and dilution by foreign races.”

He was suspected of being a Nazi sympathizer, most importantly by FDR, and while it was never really proven, The Plot Against America plays heavily on those suspicions. It doesn’t help that, in 1938, Lindbergh was given a medal of honor in Berlin on behalf of Hitler himself.

Folk singer Woody Guthrie wrote a scathing song about Lindbergh’s political aspirations titled “Lindbergh” that accused him of wanting to sell out to Hitler, and of being his puppet in America, . “They say ‘America First,'” Guthrie’s lyrics warn in the song, “but they mean ‘America Next!'”

So, while historically Lindbergh moved on from politics, he and the America First Committee were a real issue, that some, including this video from the Smithsonian Institute, have directly connected to the rise of Nazism in the U.S. The Plot Against America is fictional, but it stems from an insidious reality.