Rep. Devin Nunes (R-Calif.) won't challenge Sen. Dianne Feinstein (D-Calif.) after all.

A day after Nunes hinted at run for the Senate, his chief of staff ruled out the possibilitiy.

"Devin is running for reelection to the U.S. House of Representatives, period," Johnny Amaral, Nunes's chief of staff, told the Sacramento Bee. "He's not running for the Senate."

Nunes would have been facing an uphill battle: While a September poll showed Feinstein as vulnerable, California is a blue state that has only become more Democratic in recent years because of the state's growing Hispanic population.

On top of that, Feinstein is well-known and fairly well-liked by independents in the state, and any Republican who wants to win in a statewide race in California needs to win independents by an overwhelming margin.

Without Nunes in the race, there are no top-tier challengers to Feinstein.