California State Senate President Pro Tem Kevin de León, right, flanked by Secretary of State Alex Padilla, answers questions at a news conference in Sacramento. (AP)

Sen. Dianne Feinstein (D-Calif.) is poised to draw a primary challenger in her bid for reelection next year: Kevin de León, president of the California State Senate, is preparing launch a U.S. Senate campaign, according to multiple people familiar with his plans.

De León represents downtown and East Los Angeles in the State Senate and serves as president pro tem, a term-limited position that he will have to relinquish after next year. He is making plans to visit Washington in the next two weeks for meetings with potential donors, according to one person helping with the planning who spoke on the condition of anonymity to speak frankly about the plans.

Another person familiar with his thinking said de León is “definitely thinking about it” and on the verge of making it official. Several other Democrats in California and Washington said they did not have direct knowledge of de León’s plans but know he has been mulling a run for several weeks.

Two aides to de León in Sacramento and Los Angeles declined to comment or didn’t return requests for comment. News of his plans was first reported by CNN.

While other Democrats may still jump into the race, a head-to-head matchup between Feinstein, 84, and de León, 50, would draw significant generational, geographical and ideological contrasts.

Feinstein is a former San Francisco mayor who’s been active in state politics since the 1970s. De León first earned political notoriety in 1994, when he helped organize in Los Angeles what was then the largest demonstration in state history against Proposition 187. A longtime member of the Appropriations, Intelligence and Judiciary committees, Feinstein is seen as a champion of women’s rights, gun control and a vocal critic of the CIA’s decision to shield a report on its interrogation techniques, but otherwise an ally of the agency. But she suggested over the summer that President Trump could “be a good president” — comments that quickly earned the ire of state Democrats — and has eagerly sought accord with Republicans in hopes of preserving Senate traditions of decorum and collaboration on judicial nominations.

De León, meanwhile, is close with organized labor and one of the state’s leading progressives who has embraced the “resistance” mantle as a vocal opponent of the Trump administration. Just this year he has championed legislation that would lead to a single-payer health-care plan in California or require presidential candidates to disclose their personal tax returns in order to appear on the ballot — a direct attack on Trump.

But de León would enter the race at a severe disadvantage to Feinstein in terms of statewide name recognition and fundraising. While she is personally wealthy and could self-finance a campaign, de León cannot transfer money he’s raised for state races into a federal campaign account.

Feinstein is California’s senior senator and the oldest U.S. senator in office. She announced plans to seek her fifth full term on Monday, ending speculation that she would retire. Feinstein first won a special election in 1992 to fill out the term of then-Sen. Pete Wilson (R), who left Washington to serve as governor.

Should he enter the race, de León would upend California Democratic politics and place added strain on national Democrats as they prepare to defend 25 Senate seats next year — including 10 in states that Trump won last year. Given Democratic dominance in the state and California’s unique jungle primary system — where the top two finishers in primary contests move on to the general election regardless of party affiliation — a crowded field means that two Democrats could face each other in November 2018. That would be a repeat of what happened in 2016, when now-Sen. Kamala Harris faced off against then-Rep. Loretta Sanchez (D-Calif.).

De León’s planning signals the pent-up ambition of several prominent Democrats in state politics. Already there’s a gubernatorial race underway to replace term-limited Gov. Jerry Brown. Three major candidates, led by Lt. Gov. Gavin Newsom, are in the mix and no major Republican has entered the fray.

Meanwhile, Attorney General Xavier Becerra, who was appointed when Harris joined the Senate, is preparing for his first statewide race, while Los Angeles Mayor Eric Garcetti is talked about as a potential Senate or presidential candidate. Rep. Linda Sanchez (D-Calif.) last week stunned party colleagues by openly suggesting that it’s time for House Minority Leader Nancy Pelosi (D), a fellow Californian, to begin preparing to step down after 14 years as head of her caucus.

Several other Democrats in California’s congressional delegation, including Reps. Barbara Lee, Karen Bass, Adam Schiff and Eric Swalwell are also seen as potential Senate candidates. So is wealthy environmentalist Tom Steyer, who is friendly with de León.

But de León is likely to be the first to jump in. A longtime immigration rights advocate, he once taught U.S. citizenship courses. His parents hail from Guatemala, but he was born in Los Angeles and raised in San Diego. He won a State Assembly seat in 2006 and jumped to the State Senate in 2010.