Schiff is entering a crowded Senate field that’s likely to test alliances in the nation’s largest state. California’s top-two primary system and heavily Democratic electorate raises the possibility that two Democrats could advance to the general election. Schiff, a prodigious fundraiser, has built up a hefty campaign war chest with over $20 million cash on hand at the end of November 2022, ahead of a certainly expensive primary campaign.

Incumbent Sen. Dianne Feinstein (D-Calif.), has repeatedly declined to announce her plans yet, but Democrats largely expect the 89-year-old Senate veteran to step aside.

In an email to supporters later Thursday, Schiff acknowledged Feinstein hadn’t yet announced her plans, but added: “We need to start preparing for the fights ahead right now.” The two have also previously discussed a potential Schiff Senate bid.

Rep. Katie Porter (D-Calif.) already entered the race and is trying to carve out a progressive lane, and Rep. Barbara Lee (D-Calif.), a longtime liberal leader, has privately signaled to her colleagues she intends to run, though she has not yet made a formal announcement.

Schiff’s specific ideology within the Democratic Party doesn’t fall neatly into one box. While Porter and Lee have both served in leadership of the Congressional Progressive Caucus, Schiff has never been a part of the group. And though he began his congressional career as a member of the fiscally moderate “Blue Dog” Democrats, he now stands further to the left than he used to — with support for liberal priorities such as the Green New Deal and Medicare for All.

“I very much view myself as a progressive,” Schiff said in an interview later Thursday, adding that he intends to stress basic quality-of-life issues like housing and wages.

Schiff, as well as Lee, are expected to be able to draw on deep connections to other California politicians, dating back to their time in the state legislature. They’ve both served alongside other members of Congress who also rose up through the state ranks.

Top House Democratic leaders are signaling they’ll remain neutral in the contest between the California heavyweights.

“I think there are a few members of the caucus who are running for the United States Senate and I wish all of them well,” House Minority Leader Hakeem Jeffries said in a brief interview Thursday. “We’re going to miss them, but I wish all of them well in their political endeavors.”