A political movement rallies against underregulated banks, widening gaps in wealth, and gridlocked governments. Sound familiar? More than a century before Occupy Wall Street, the People’s Party of the 1890s was organizing for change. They were the original source of the term “populism,” and a catalyst for the later Progressive Era and New Deal.

Historians wrote approvingly of the Populists up into the 1950s. But with time and new voices, led by historian Richard Hofstadter, the Populists were denigrated, depicted as demagogic, conspiratorial, and even anti-Semitic.

In a landmark study, Walter Nugent set out to uncover the truth of populism, focusing on the most prominent Populist state, Kansas. He focused on primary sources, looking at the small towns and farmers that were the foundation of the movement. The result, The Tolerant Populists, was the first book-length, source-based analysis of the Populists. Nugent’s work sparked a movement to undo the historical revisionism and ultimately found itself at the center of a controversy that has been called “one of the bloodiest episodes in American historiography.”

This timely re-release of The Tolerant Populists comes as the term finds new currency—and new scorn—in modern politics. A definitive work on populism, it serves as a vivid example of the potential that political movements and popular opinion can have to change history and affect our future.