Borah's legal practice had made him prominent in southern Idaho, and in 1902 he sought election to the Senate. By this time, a united Republican Party was deemed likely to defeat the Democratic/Populist combine that had ruled Idaho for the past six years. The 1902 Idaho state Republican convention showed that Borah had, likely, the most support among the people, but the choice of senator was generally dictated by the caucus of the majority party in the legislature. In the 1902 election, Republicans retook control, electing a governor of their party, as well as the state's only House member and a large majority in the legislature. Three other Republicans were seeking the Senate seat, including Weldon B. Heyburn, a mining lawyer from the northern part of the state. When the legislature met in early 1903, Borah led on early caucus ballots, but then the other candidates withdrew and backed Heyburn; he was chosen by the caucus, and then by the legislature. There were many rumors of corruption in the choice of Heyburn, and Borah determined that the defeat would not end his political career. He decided to seek the seat of Senator Dubois (by then a Democrat) when it was filled by the legislature in early 1907.