The California Democratic Party declined to endorse incumbent Sen. Dianne Feinstein (D-CA) for re-election at its annual convention in San Diego early Sunday.

The party did not endorse a candidate in the gubernatorial election, either, where frontrunners Lt. Gov. Gavin Newsom and former Los Angeles mayor Antonio Villraigosa are neck-and-neck. But the party’s refusal to back Feinstein is seen as an “embarrassing rebuke” to a long-time party stalwart.

It is also seen as a boost for State Senate President pro Tem Kevin de León (D-Los Angeles), who has lagged in the polls but has earned the endorsement of left-wing groups as he mounts a “progressive” challenge to Feinstein.

The Los Angeles Times reports:

Though De León did not get the endorsement, his success in blocking Feinstein from receiving it shows that his calls for generational change and a more aggressively liberal path have resonated with some of the party’s most passionate activists. Feinstein has never been a state party glad-hander, while De León has cultivated relationships with the party’s delegates. He still faces a significant challenge in trying to topple Feinstein, who trounces De León in all public polling and fundraising. … A candidate had to capture 60% of the delegates’ votes to win the party’s seal of approval, considered unlikely given the field of politicians in the race with deep ties to the state party.

Bay Area public radio station KQED notes that the two candidates, and their supporters, presented sharp contrasts at the convention:

Feinstein has always been a little to the right of where the party’s activists are. Now, at age 84 and in her final campaign, Feinstein is once again at odds with progressives, despite her efforts to move left by more strongly opposing President Donald Trump’s agenda. … In his speech to the convention, de León reminded the crowd that his opponent hasn’t always been a reliable liberal. “Democrats, you’ll never have to guess where I stand,” de León said before noting he’s championed issues such as raising the minimum wage, single-payer health care and the environment.

Feinstein is still favored to win the June 5 primary, but will likely face De León again in the general election in November, given the state’s “top two” or “jungle” primary system.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He was named to Forward’s 50 “most influential” Jews in 2017. He is the co-author of How Trump Won: The Inside Story of a Revolution, is available from Regnery. Follow him on Twitter at @joelpollak.