Important structural changes included the direct popular election of senators according to the Seventeenth Amendment, ratified on April 8, 1913, with positive effects (senators more sensitive to public opinion) and negative effects (undermining the authority of state governments). Supreme Court decisions based on the Constitution's commerce clause expanded congressional power to regulate the economy. One effect of popular election of senators was to reduce the difference between the House and Senate in terms of their link to the electorate. Lame duck reforms according to the Twentieth Amendment reduced the power of defeated and retiring members of Congress to wield influence despite their lack of accountability.