Rep. Jim Costa (D) has his first challenger in the Central Valley 20th district.

Josh Miller (R), a 27-year-old conservative activist from Visalia who is a salesman for a produce logistics company, recently announced his intention to run.

Miller, a former church missionary, campaigned last year for Proposition 8, the measure overturning the state’s gay marriage laws. He said he has been influenced by the talk-radio hosts he listened to with his father while he was growing up.

“Josh Miller is definitely passionate about his country as well as the future of California,— a biographical entry on Miller’s campaign Web site says. “Defining himself as a Roosevelt Republican (Theodore Roosevelt), thinking of the people before the party — Josh’s belief is that the mantle needs to be passed to the next generation for a new cultivation of American Prosperity.—

The 20th district was recently considered competitive territory but has dramatically trended toward the Democrats in the past few election cycles. Since winning the seat with 53 percent in 2004, Costa has glided to re-election.