Setting up a bruising intra-party battle between a left-leaning state leader and a veteran of California politics, state Senate President Pro Tem Kevin de León announced Sunday that he would challenge U.S. Sen. Dianne Feinstein in 2018.

De León will be Feinstein’s first major Democratic opponent since she was elected to the Senate in 1992.

“The state has changed significantly over the past 25 years, and we’re long overdue for a real debate on the issues, priorities and leadership the voters want from their senator,” De León said in an interview Sunday morning. “California deserves to have a choice.”

Feinstein, who said last week she will run for re-election, has racked up declarations of support from a host of top California Democrats.

But liberal activists who accuse her of not being tough enough on President Donald Trump have been waiting for a progressive like De León, who is known for his advocacy for single-payer health care, climate change measures and California’s recently passed “sanctuary state” bill.

“You’ll see a clash, which is in part generational, in part ideological, in part style,” said Bill Whalen, a fellow at Stanford University’s Hoover Institution. “She’s not one for theatrics or angry denunciations.”

De León, 50, grew up in San Diego as the son of a single mother from Guatemala, and dropped out of college to work as a community organizer with an immigrant rights group. He later graduated from Pitzer College in Claremont.

He has represented Los Angeles in the state Assembly and Senate since 2006, and served as Democratic leader in the Senate for three years. The first Latino to lead the Senate in more than a century, he will be termed out of office and won’t be able to run for re-election in 2018.

Bill Carrick, a Feinstein campaign strategist, downplayed De León’s challenge. “He’s a term-limited politician looking for a gig,” Carrick said. “He’s going to find out that Dianne Feinstein is a pretty big hill for him to climb.”

In his first campaign video, released Sunday, De León focused on his personal story, without mentioning Feinstein.

He will hold a formal campaign kickoff event Wednesday afternoon at Los Angeles Trade Technical College.

A recent Public Policy Institute of California poll found that while Feinstein, 84, has high approval ratings, a majority of likely California voters would prefer her to retire and not run again. She was booed earlier this year in San Francisco when she urged patience for Trump and said he “could be a good president” if he changed his approach.

But Feinstein has wide support from state leaders. She’s received endorsements from her Senate colleague Kamala Harris, former Sen. Barbara Boxer, House Minority Leader Nancy Pelosi, Lt. Gov. Gavin Newsom, Los Angeles Mayor Eric Garcetti, San Francisco Mayor Ed Lee, Rep. Adam Schiff, Rep. Ted Lieu and state Secretary of State Alex Padilla.

On Sunday morning, De León received a quick endorsement from Rep. Ro Khanna, D-Fremont, and the national progressive group Democracy for America, as well as tweeted declarations of support from two Democratic state lawmakers, Assemblyman Kevin McCarty and Assemblywoman Lorena Gonzalez Fletcher.

“I have been particularly impressed with Kevin’s passion for creating pipelines for Latino and African-American kids for jobs in Silicon Valley,” Khanna said in a text message. “He’ll bring new ideas to the Senate, and I am proud to endorse him.”

He may not be the only Democrat to challenge Feinstein, who is the oldest member of the U.S. Senate. San Francisco philanthropist Tom Steyer and Los Angeles entrepreneur Joe Sanberg are both considering a Senate run.

“Everyone who runs against Dianne Feinstein is going to be reminded that she didn’t get there by baking cupcakes and being a softy,” said Kevin Eckery, a Republican strategist in Sacramento. He pointed out that De León has limited name recognition statewide.

One of De León’s biggest challenges will be fundraising. While he has more than $2.8 million in a state campaign account, he can’t use that in a run for federal office. And party donors might be reluctant to support a Feinstein challenge. “I imagine Feinstein’s people will keep a note of every Democrat who gives money to him,” Whalen said.

California’s top-two primary system is another obstacle. Even if De León finds support among Democrats, he’d have to defeat Feinstein among the broader state electorate in November.

“If he were to run against her in a closed primary with very small turnout, there’s a chance lightning could strike and he could beat her,” Whalen said. But in a general election matchup, he said, “Republicans are not going to elect Kevin de León.”

While De León is unlikely to topple Feinstein, a statewide race will help him elevate his name recognition and position himself as one of the leaders of California’s progressive wing. He also doesn’t have many other options of elected offices to run for.

No major Republican elected officials in the state have said they’re considering a Senate run. De León’s entry raises the possibility of a November ballot with a governor’s race and a Senate race between two Democrats. Some polls of the 2018 governor’s race show two Democrats getting first and second place in that primary.

That could have a dire impact for the GOP on lower-ballot races like crucial Congressional races. “The challenge is how you turn out Republican voters where there’s only a handful of places where they’ll be able to elect a Republican,” Eckery said.

On the other hand, an expensive intra-party war in the Senate race could drain funding from Democrats challenging Republican House members, especially in the seven GOP districts won by Democrat Hillary Clinton in 2016.

De León said that wouldn’t be the case. “The resources will be there for those seven seats,” he said. “Going up against a longtime incumbent and the political establishment wont be easy, but this state needs a different and new kind of leadership.”