Clark's long-standing dream of becoming a United States Senator resulted in scandal in 1899 when it was revealed that he bribed members of the Montana State Legislature in return for their votes. At the time, U.S. Senators were chosen by their respective state legislators. The corruption of his election contributed to the passage of the 17th Amendment. The U.S. Senate refused to seat Clark because of the 1899 bribery scheme, but a later senate campaign was successful, and he served a single term from 1901 until 1907. In responding to criticism of his bribery of the Montana legislature, Clark is reported to have said, "I never bought a man who wasn't for sale."