populism (n.)

1893, "political doctrines or principles of the Populist Party," a left-wing agrarian faction in U.S. politics; see populist + -ism. After the movement faded the word was applied in other contexts (for example a French literary trend of the 1930s), and from the 1960s it was used for political movements that sought to rally ordinary people who see their concerns as being disregarded by established parties and elites, but it also is used pejoratively for irrational or simplistic demagoguery.