Thompson, whose hometown of St. Helena had shifted from the 4th District into the 2nd after reapportionment, ran in the 1993 special election for Keene's seat.

[9] National Democrats approached Thompson about running for Congress in 1996 against freshman Republican Frank Riggs.

Riggs did not seek reelection to his House seat and made an unsuccessful bid for the United States Senate.

[10] Thompson was elected by almost a 30% margin[11] and has been reelected ever since without substantive opposition,[11] turning what was a swing district for most of the 1980s and '90s into a fairly safe Democratic seat.

[citation needed] For his first seven terms, Thompson represented a district stretching from the far northern part of the San Francisco Bay Area all the way to the North Coast.

[13] Thompson voted with President Joe Biden's stated position 100% of the time in the 117th Congress, according to a FiveThirtyEight analysis.

[20] Thompson voted for President George W. Bush's Healthy Forests Initiative,[21] which some environmentalists saw as a favor to the timber industry.

[29][30] In March 2012, Thompson and state Assemblyman Jared Huffman voiced their opposition to a piece of water legislation that the House would be voting on, which Thompson argued would "kill local jobs, ignore 20 years of established science and overturn a century of California water law.

"[31] In late 2002, Thompson joined Representatives Jim McDermott and David Bonior on a fact-finding trip to Iraq.

They expressed skepticism about the Bush administration's claims that Iraqi President Saddam Hussein was stockpiling weapons of mass destruction.

Local Napa Valley wineries often sponsor Thompson's campaigns with lunches, dinners, wine tastings and tours.