William Mahone
In 1887, Virginia's General Assembly elected Daniel as a Democrat to the United States Senate to succeed Readjuster Republican William Mahone. He was reelected four times: in 1891, 1897, 1904, and 1910. Thus, he served from March 4, 1887 until his death, largely cooperating with the Democratic organization created by his fellow U.S. Senator Thomas S. Martin.