A year after President Joe Biden’s inauguration, around two-thirds of Republican voters believe his election was illegitimate, and the idea that the 2020 election was stolen from Donald Trump is now a defining issue of the Republican Party. Yet the story of how lies about election fraud made their way to the center of American politics has not been fully told.

In a new investigative collaboration, FRONTLINE and ProPublica trace the hidden sources of misinformation about the 2020 election, demonstrating how a handful of people have had an outsized impact on the current U.S. crisis of democratic legitimacy.