California Democrats sent a loud message to incumbent Sen. Dianne Feinstein, one of the nation’s best-known and longest-serving politicians, by not endorsing her for re-election at their state convention Sunday.

The delegates also offered no endorsement in the state’s race to replace termed-out Gov. Jerry Brown. Lt. Gov. Gavin Newsom receiving the most support, with 39 percent of the delegates backing him, followed by treasurer John Chiang (30 percent), former state superintendent of public instruction Delaine Eastin (20 percent) and former Los Angeles Mayor Antonio Villaraigosa — who is near Newsom at the top of recent polls — finishing far back with 9 percent of the support.

But the big shocker was the delegates’ rejection of Feinstein.

Even though the 2,775 delegates who cast ballots in the Senate endorsement race fell short of the 60 percent threshold needed to endorse her opponent, state senator Kevin de León, D-Los Angeles, 54 percent backed the challenger versus only 37 percent who supported Feinstein.

“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 Sunday. “California Democrats are hungry for new leadership that will fight for California values from the front lines, not equivocate on the sidelines.”

Analysts said the vote was a message pitch to Feinstein, who was elected to the Senate 1992 and was first elected to public office in 1969 as a member of the San Francisco Board of Supervisors.

“The Democratic Party tends to endorse incumbents,” said Rose Kapolczynski, a veteran California Democratic strategist who ran former Sen. Barbara Boxer’s 2010 successful re-election campaign.

“It sends a message that the Democratic Party is a progressive party and they’re going for the candidate who they view is the more progressive candidate,” said Tom Steyer, the billionaire San Francisco activist who is close with de Leon but has not endorsed in the race. “Both of them have long histories of service to the state, to the country and to the party. And it’s pretty clear that Kevin is positioned as more progressive than Senator Feinstein.”

But the long-term value might be limited. Feinstein’s camp and others say that the delegates are generally more progressive than the larger voting universe.

While the Democratic nod would enable de Leon to draw on the party’s infrastructure and some of its cash, the fundamentals of the race would still be largely the same. Feinstein leads de Leon 46 percent to 17 percent in a January survey by the nonpartisan Public Policy Institute of California. Nearly two-thirds of likely Democrat voters prefer Feinstein. She has 96 percent name recognition with voters, while two-thirds don’t know de Leon. Plus, with nearly $10 million cash on hand — nearly 20 times more than de Leon — and millions more in personal wealth to tap, Feinstein tops de Leon in a category where he is finding it hard to compete.

Still, the delegates vote will give a short-term adrenaline boost to his campaign.

“Winning an endorsement, or even holding Senator Feinstein to a draw by denying this incumbent her party's endorsement, would be a coup for Kevin de Leon,” Thad Kousser, a professor of political science at UC San Diego who has studied the effect of endorsements, said before the results were announced.

“It would be a surprising sign that California's Democratic establishment is not lining up behind one of its most experienced and popular officeholders,” Kousser said. “But it would not be a death knell.”

Feinstein has been here before. In 1990, she was booed at the state party convention when she came out in support of the death penalty when she was seeking the party’s nomination for governor. The party endorsed the more liberal state attorney general John Van de Kamp. It didn’t matter as Feinstein won the primary, but lost the general election to Republican Pete Wilson.

In the governor’s race, it was not expected that any candidate would get more than the 60 percent threshold needed to secure the endorsement. However, the race showed that delegates have a different opinion of the candidates than voters responding to polls.

Newsom, with 23 percent of the vote and Villaraigosa with 21 percent are the top two candidates in the June primary for governor, with 24 percent of likely voters undecided, according to a survey conducted by the nonpartisan Public Policy Institute of California. Chiang had 9 percent in that survey, while Eastin had 4 percent. Republican Assemblyman Travis Allen, R-Huntington Beach, had 8 percent, GOP businessman from Rancho Santa Fe John Cox had 7 percent and former Sacramento area GOP Rep. Doug Ose 3 percent.

On Saturday, Los Angeles Mayor Eric Garcetti, who has endorsed Feinstein, downplayed the value of endorsements in high profile races.

“While these are important for the base of activists, I think most people don’t look at many endorsements,” Garcetti said after addressing the delegation. “For those high level races, they figure out who you are. I think it’s important for this activist base, but I don’t think it decides elections.”

Then Garcetti paused and said with a smile. “ I don’t know if I should say that at the California Democratic Party convention.”