Davidson was elected district attorney of Green Lake County in 1888. He served as chairman of the Republican congressional committee for the sixth district of Wisconsin in 1890. He moved to Oshkosh, Wisconsin, on January 1, 1892, and continued the practice of law. He was appointed city attorney in May 1895 for two years.
Davidson was elected representative of Wisconsin's 6th congressional district as a Republican to the Fifty-fifth and to the two succeeding Congresses (March 4, 1897 – March 3, 1903). He served as chairman of the Committee on Railways and Canals (Fifty-sixth through Sixty-first Congresses). From the Fifty-eighth Congress Davidson redistricted and was elected as the representative of Wisconsin's 8th congressional district and was reelected to the four succeeding congresses in the same role (March 4, 1903 – March 4, 1913) He was an unsuccessful candidate for reelection in 1912 to the Sixty-third Congress and for election in 1914 to the Sixty-fourth Congress. For the Sixty-fifth Congress Davidson was once again elected as the representative of Wisconsin's 6th district serving from March 4, 1917, until his death in Washington, D.C., on August 6, 1918. He died of heart disease[1][2] and was interred in Riverside Cemetery in Oshkosh, Wisconsin. On April 5, 1917, he was one of the 50 representatives who voted against declaring war on Germany.