Gibson worked as a professor of medical jurisprudence at the Tennessee Medical College from 1889 to 1906. Congress Gibson's law partner, Leonidas Houk, was elected to the 2nd district seat in the U.S. House of Representatives in 1878, and served throughout the 1880s. During this period, Houk developed a political machine that largely controlled the state Republican Party, and established Republican dominance in the 1st and 2nd districts. Gibson, who remained a close confidant of Houk, was influential within the Houk machine, and was considered by many Houk's rightful successor following the congressman's sudden death in 1891. He lacked the organization to mount a campaign, however, and Houk's son, John Chiles Houk, was elected to the congressional seat. In 1893, Gibson launched his campaign for the 2nd district seat. The younger Houk's popularity had declined when evidence surfaced that he had helped ensure the defeat of Houk machine rival Henry Clay Evans in the 3rd district. Historian Gordon McKinney described the contest between Gibson and Houk for the Republican nomination as "one of the dirtiest in East Tennessee history." Houk assailed Gibson's war record, and managed to have Gibson expelled from the Grand Army of the Republic (the GAR determined Gibson had been a civilian employee, not a soldier). Gibson accused Houk of frequently missing votes, including a key vote on a veterans' pensions bill, and argued that the silence of politicians like Houk on the tariff issue was to blame for the Panic of 1893. In the March primary, Gibson edged Houk, 14,072 votes to 13,119. Houk refused to drop out, and opposed Gibson as an independent in the general election, but again was defeated, 16,215 votes to 13,191 (the Democrats did not field a candidate). Gibson supported protectionist measures, such as tariffs on imports, and generally supported prohibition. In January 1896, he introduced a bill that would have provided pensions for survivors of the steamboat Sultana disaster, though the bill was never passed. He voted for the declaration of war with Spain in April 1898. On June 14, 1898, he delivered a speech on the House floor calling for the annexation of Hawaii and the construction of the Nicaragua Canal. During the intraparty fighting between Walter P. Brownlow and Henry Clay Evans for control of the state Republican Party, Gibson aligned himself with Brownlow. In 1902, Nathan W. Hale, who was supported by the Evans faction, challenged Gibson