People in the Populist party had interest in the free coinage of silver, were mostly created by labor and farmers, wanted a graduated income tax, and government control of monopolies.
Once the party lost the election of 1896, they did not have much money or faith to run again in 1900. The party diminished very soon after the 1896 election.
The Populist Party was not successful in achieving any of its own agenda, it did however play a major role in influencing the Progressive Party which passed many Populist reform bills.