In 1918, he sought re-election as a Democrat to the Sixty-sixth Congress, and continued as a Democrat through the ensuing five congressional elections, all of them uncontested. Martin thus served in Congress from March 4, 1915 until his death in Washington, D.C., on April 6, 1929. He was a delegate, representing his congressional district, to the 1920 Democratic National Convention in San Francisco. Martin was an Episcopalian as well as a Freemason.