Final answer:
The direct election of U.S. senators resulted from political pressure by the Progressives, leading to the Seventeenth Amendment's ratification in 1913, which mandated the popular vote selection of senators.
Explanation:
The direct election of U.S. senators came about due to political pressure from the Progressives. The Seventeenth Amendment, ratified in April 1913, mandated that senators would be elected by popular vote in each state, mirroring the election process for House of Representatives members. This change shifted the selection of senators from state legislatures to the direct choice of the people, enhancing citizen participation in the electoral process.
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