As a prominent and respected newspaper editor, Glass often supported candidates who ran against Virginia's Democrats of the post-Reconstruction period, who he felt were promoting bad fiscal policy. In 1896, the same year his father died, Glass attended the Democratic National Convention as a delegate, and heard William Jennings Bryan speak. Glass was elected to the Senate of Virginia in 1899, and was a delegate to the Virginia constitutional convention of 1901–1902. He was one of the most influential members of the convention, which instituted measures associated with the Progressive movement, such as the establishment of the State Corporation Commission to regulate railroads and other corporations, replacing the former Virginia Board of Public Works.