William E. Borah came to Idaho as a young lawyer in 1890. He quickly became prominent both as a lawyer and politician in the Republican Party. Borah was a friend and political colleague of Steunenberg, even though they were members of different political parties. He delivered the eulogy at Steunenberg's funeral.
In early 1907, Borah was elected by the Idaho legislature to be the new U.S. Senator from Idaho. This was before the Seventeenth Amendment, and just a few months before the Haywood trial began. Borah delayed taking his seat in the Senate so he could help try the Haywood case.
It is noteworthy that Borah opposed trying the officials of the Western Federation of Miners in Idaho, preferring to try only Orchard, and leaving the prosecution of the union officials to Colorado. But, other Idaho officials felt differently and prevailed.
A complicating factor for Borah was that during the pendancy of the Haywood case before trial, he was charged in federal court with timber fraud, based on his being the general counsel for the Barber Lumber Company, which had allegedly acquired timber claims in violation of federal law. Coincidentally, Steunenberg was one of the principals of the Barber Lumber Company. Through the intervention of President Teddy Roosevelt, Borah's trial was postponed until after the Haywood trial. Borah was tried shortly after Haywood was acquitted in 1907. He was defended by Hawley and was himself quickly acquitted.
After he took his seat in the U.S. Senate, Borah quickly became a respected member of that body. From 1924 to 1933 he was chair of the Senate Foreign Relations Committee. In 1936, Borah, "the Lion of Idaho," was an early contender for the Republican nomination for the presidency of the United States, but did not get the nomination.