Thompson was approached by national Democrats about running for U.S. Congress in 1996 against freshman Republican Frank Riggs. Thompson's state senate district was virtually coextensive with the congressional district. However, Thompson declined, believing his senate seniority would be more beneficial to his district than would his being a freshman U.S. congressman. In 1998, however, Thompson was due to be termed out of the state senate, and opted to run against Riggs after all. Riggs opted to retire and make an unsuccessful bid for United States Senate. Thompson won by almost a 30% margin. He has been reelected ten times with no substantive opposition, and has turned what was a swing district for most of the 1980s and 1990s into a fairly safe Democratic seat.