As the Silver Republican faction declined, it was thought by many that Dubois' political career was over. But in 1900, after refusing to rejoin the Republican Party, he was elected again to the United States Senate by the Democratic Idaho Legislature by defeating Shoup, his onetime political ally. Shortly after returning to the Senate in 1901, Dubois
switched parties and joined the Democratic Party, one of few politicians in that era to do so. He remains the only person in Idaho history to serve in the
United States Congress as both a Republican and a Democrat. During his second term in the Senate, Dubois continued to advocate abandoning the gold standard, but focused most of his attention on opposition to
imperialism and
Mormonism. Dubois led a group of senators which tried to force
Reed Smoot of
Utah, the first Mormon ever elected to the Senate, to resign. Dubois strongly opposed efforts to make the
Philippines, which were annexed from
Spain after the
Spanish–American War, an American territory. Dubois first supported independence for the Philippines, but after a 1905 visit, he declared that Filipinos could not rule themselves and advocated selling the islands to
Japan. His reasons for opposing Filipino independence were strongly influenced by racist beliefs. He was afraid of the new territories' economic competition with the rest of America, but not because he believed that the Filipinos presented an economic threat. Dubois disparaged Filipinos and many other ethnic and racial groups, declaring that "It is difficult to get the Filipino to labor at all," and asserting that "The Hawaiians will not labor . . . They are very similar to our American negro." The Philippines posed an economic threat if Japanese laborers migrated there, but he hoped that trade barriers could prevent Philippines sugar and tobacco from reaching American markets. Dubois also supported strong limits on
Chinese immigration. Dubois broke with most Democrats of the day and supported President
Theodore Roosevelt's agenda of environmental
conservationism. He supported
William Randolph Hearst for the Democratic presidential nomination in 1904. ==Defeat and later years==