Senate. In 1864 he became President of the state Senate and served in that position until 1866. Because United States Senators were elected by the state legislatures during his lifetime, and that was the only office that Mitchell was to seek, this early position in the state Senate was the only popularly elected office that he would ever run for or win. Mitchell was an unsuccessful candidate for the United States Senate from Oregon in 1866, losing to Henry W. Corbett. He tried again in 1872 and this time won, taking office in 1873. He petitioned to officially change his name after he was elected. On the topic of names, during Mitchell's second period of Senate service (from November 18, 1885, to March 3, 1897), he concurrently served alongside two other different individuals named "John Mitchell", from other states. From November 18, 1885, to March 3, 1887, Mitchell served alongside Sen. John I. Mitchell from Pennsylvania; and from March 4, 1893, to March 3, 1897, Mitchell served alongside Sen. John L. Mitchell from Wisconsin. By this time, he had married again, but had not divorced the woman he had married in Pennsylvania. His opponents tried to block him from becoming a senator by asking a Senate committee to expel him for what he had done in the past, charging him with bigamy, desertion and living under an assumed name. Though these charges were certainly true, the Senate Committee decided they were not relevant. Mitchell served in the Senate from 1873 to 1879, and was defeated for reelection. He ran for reelection to the Senate in 1882 but lost. In 1885, however, he was elected again to the Senate, and reelected in 1890. Mitchell sought reelection by the Oregon Legislature in 1897, but his candidacy proved to be highly divisive: the resulting scandal prevented the 19th Oregon Legislative Assembly from organizing and, consequently, left Oregon with a vacant U.S. Senate seat for nearly two years. Joseph Simon was ultimately chosen for the seat. While not in the Senate, Mitchell practiced law. Mitchell's last term in the Senate began in 1901 and was to last until 1907, but Mitchell died before it expired. Mitchell was devoted to business interests and was against the populists and their political reforms. In the Senate, he was interested in transportation issues. He was chairman of the committee on railroads from 1877 to 1879 and from 1889