21st District

Matchup: Rep. David Valadao (R) vs. Emilio Huerta (D)

Dynamic: The district is 71% Latino, giving Democrats hope of toppling the congressman. Valadao won 54% of the vote in the primary as an incumbent, and voters there can be conservative when it comes to economic and local issues. The last Democrat to challenge Valadao in 2014 suffered an embarrassing landslide defeat. Huerta, a labor lawyer, is hoping a grassroots campaign that capitalizes on his local family ties can counter those forces. This is among the places to watch for whether Republican presidential nominee Donald Trump will have an effect on down ballot races. Race rating: Favored Republican

Interesting fact: Huerta is the son of the labor rights icon Dolores Huerta. Valadao is the poorest member of Congress thanks to debt owed by his family farming business.