Final answer:
The Populist Party influenced twentieth-century politics through its ideas and reforms, despite its decline as a separate political entity.
Step-by-step explanation:
The Populist Party had a significant influence on twentieth-century politics, even after its decline. While the party itself disappeared by 1900, many of its ideas were adopted by the Republicans and Democrats during the Progressive Era. The Populist Party called for the regulation of railroads, an income tax, and the popular election of U.S. senators. These ideas shaped the political landscape and led to reforms in the following decades.
Furthermore, the Populist Party's decline was not solely due to its defeat in the elections. Other factors, such as the discovery of gold deposits and the Spanish-American War, also contributed to the decline. However, the Populist spirit remained, and the reformist zeal took on new forms as the twentieth century unfolded, continuing to influence politics.
In conclusion, while the Populist Party may have declined as a separate political entity, its ideas and influence persisted in twentieth-century politics, as they were adopted by other parties and shaped the political landscape of the Progressive Era and beyond.