Now THAT'S a good question!
The populists were a party mostly consisting of small farmers who were opposed to the rapid changes and industrialization of American society back in the late 1800s. Specifically, they called for the abolition of national banks, a graduated income tax, direct election of Senators, civil service reform, a working day of eight hours and Government control of all railroads, telegraphs, and telephones.
They managed to get the civil service reform, 8 hour days, and direct election of Senators, who, before then, were appointed by state legislatures.