In a stunning - if not altogether unexpected - blow to long-time California Senator Dianne Feinstein, the top Democrat on the Senate Judiciary Committee, the California state Democratic Party opted not to endorse their own senior senator as she prepares to start campaigning to defend her seat in the 2018 midterms.

Delegates to the state party convention instead favored progressive state Senate leader Kevin de León, over Feinstein by a 54% to 37% margin, according to results, which were announced early Sunday. And while neither candidate reached the 60% threshold required to receive the party endorsement outright for 2018, de Leon's camp claimed it as a profound victory.

“The outcome of today’s endorsement vote is an astounding rejection of politics as usual, and it boosts our campaign’s momentum as we all stand shoulder-to-shoulder against a complacent status quo,” de León said in a prepared statement, quoted by Politico. "California Democrats are hungry for new leadership that will fight for California values from the front lines, not equivocate on the sidelines."

Feinstein, a longtime centrist, has often maintained an uneasy truce with the progressive activists who dominate the state party. The result followed two days of lobbying by the candidates in convention speeches and throughout the convention halls.

In an appeal to thousands of delegates Saturday, de Leon portrayed Feinstein as a Washington power broker and corporatist insider who wouldn't listen to progressives.

Still, the state party's refusal to endorse Feinstein will ultimately have little impact on her chances of winning another term later this year. Every poll still shows her winning the race by a wide margin.

But her challenger de Leon is undeterred by the unfavorable numbers:

"I’m running for the U.S. Senate because the days of Democrats biding our time, biting our tongue, and trying to let it work the margins are over," he said to cheers. "I’m running because California’s greatness comes from paths of human audacity, not congressional seniority." The non-endorsement appears unlikely to immediately alter the trajectory of a contest Feinstein is leading by a wide margin. First elected in a 1992 special Senate election, Feinstein is out-polling de León 46 percent to 17 percent among likely California voters, according to the most recent poll by the Public Policy Institute of California. Her financial advantage is even more overwhelming: Feinstein held close to $10 million in cash on hand at the end of last year, while de León reported raising just $500,000.

Feinstein, who was one of the sponsors of the Clinton-era assault weapons ban, touted her gun-control bona fides, and stressed the importance of California Democrats maintaining unified support.

California Democrats, she said, have “the largest delegation in the House. You’ve got Kamala Harris and me in the Senate.” She said Democrats can more effectively advance their principles “if we have unified support.” Feinstein lost the state party endorsement to a rival Democrat, John Van de Kamp, when she ran for California governor in 1990. And though supporters this year waved signs and stopped Feinstein to pose for photographs, she at times appeared out of step working the convention halls. Interrupted in her convention speech Saturday by music signaling her time to speak had run out, Feinstein said, "I guess my time is up." As she left the stage, de León supporters in the crowd yelled back at the 84-year-old, "Time’s up! Time’s up!" The state party returned a non-endorsement in California’s other major statewide contest, as well. In the race for governor, Lt. Gov. Gavin Newsom led all candidates with 39 percent support, followed by state Treasurer John Chiang and former state schools chief Delaine Eastin with 30 percent and 20 percent, respectively. Former Los Angeles Mayor Antonio Villaraigosa, who has drawn close to Newsom at the top of statewide public opinion polls, finished a distant fourth, at 9 percent.

It's worth highlighting that Feinstein's circumstances in the 2018 race mirror - to a degree - the circumstances that Hillary Clinton faced during the 2016 campaign. Both represent a Democratic establishment that has failed to energize the progressive voters. And both reportedly have trouble connecting with voters.

We wonder: Could Feinstein, whose seat is viewed as "safe" by pollsters, be in for an upset, either by her Republican opponent, or a progressive insurgency? For the guaranteed answer, we await the NYT and WaPo polls showing that Feinstein is a 99% favorite to win.