The incumbent Democratic congressman and a challenger from the same party established themselves as the most formidable candidates for California's 4th District House seat heading into the June 2 primary election.

Rep. Mike Thompson, D-St. Helena, has held the 4th District seat in Congress since he was first elected in 1998, but now faces well-funded competition from his own party. Eric Jones, a former venture capitalist and political newcomer, out-raised the longtime congressman.

The field includes seven other candidates, including five Republicans, most of whom have not established significant fundraising or campaign presence. Raymond Riehle, a Republican from Citrus Heights, switched his campaign from the 6th District to the 4th District, and raised more than his GOP competitors.

The jungle primary pits all candidates — regardless of political affiliation — against one another for the two-year term, with the two top vote-getters advancing to the general election in November.

Where is the district?

The 4th District stretches from the Napa Valley through Yolo County and into the Sacramento Valley, encompassing the conservative counties of Sutter, Yuba and Colusa under newly drawn congressional maps reshaped by the passage of Prop. 50.

The district expanded from five to nine counties, and remained primarily blue despite the conservative territories swept into its boundaries.

Who are the candidates?

Rep. Mike Thompson, D-St. Helena, was first elected to Congress in 1998, and won reelection to each term since. Thompson, 75, currently serves on the House Committee on Ways and Means, where he is ranking member of the Subcommittee on Tax and a senior member of the Health Subcommittee. Before his time in Congress, he served in the state Senate, where he became the first Vietnam veteran elected, according to his campaign website.

Eric Jones was raised in Maine and graduated from Yale before beginning his career as a venture capitalist in San Francisco. The 35-year-old later moved to Napa with his wife to raise their two children. He founded the American Dream Institute, a nonprofit focused on constructively engaging young people, and campaigned on a working-class message of affordability, greater access to childcare and healthcare, and properly taxing billionaires and corporations, according to his campaign website.

Raymond Riehle, a Republican from Citrus Heights, owns a small business, A-Applied Mailing Service. He originally campaigned for the 6th District, but filed for the 4th District after Rep. Kevin Kiley opted to run for the 6th District seat. He campaigned on conservative values and in opposition to Democratic policies supported by liberal members of Congress, according to his campaign website.

Who is funding the race?

Jones has raised more than $3.2 million as of the latest campaign filings, about a quarter-million more than Thompson, who has raised nearly $3 million as of the most recent Federal Elections Commission filings in mid-April.

Vowing not to accept donations from corporate political action groups, Jones put $364,000 into his own campaign, and raised more than $2.8 million from individual contributors. Thompson received nearly $1.6 million from individuals, and more than $1.3 million from a variety of political action committees and other collectives.

Riehle raised more than $108,000, and none of the other candidates raised more than $15,000 as of the mid-April reports.

Who else is supporting the candidates?

Thompson has a long list of endorsements, including senators and representatives in Congress, Gov. Gavin Newsom and state lawmakers. Local officials and community leaders, particularly throughout the carry-over parts of the district, have also endorsed the incumbent.

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