She is one of California’s most recognizable politicians, an icon in the Democratic Party, and the second longest-serving U.S. senator in Golden State history. But a new poll is raising the volume of one of the most intriguing questions in political circles from here to Capitol Hill: Is Dianne Feinstein losing her ironclad grip on her Senate seat?

A new poll found just 41 percent of likely California voters back the 84-year-old, five-term incumbent in her bid for re-election, six months before the 2018 primary.

The poll, released Wednesday by the UC Berkeley Institute of Governmental Studies, put Feinstein still comfortably ahead of her closest rival, state Senate leader Kevin de León, who received support from 27 percent of voters. Nearly a third of respondents, 32 percent, said they were undecided.

But for Feinstein, a virtual shoo-in in her previous re-election bids, dropping below 50 percent “shows weakness and vulnerability, much more so than in any of her past re-election campaigns,” said Mark DiCamillo, the head of the IGS poll.

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A surprisingly high number of voters also say they have a negative impression of Feinstein — 42 percent, compared to 45 percent who think of her positively.

The biggest winner of the poll might be somebody whose name wasn’t even part of the survey: Tom Steyer, the Democratic megadonor behind a high-profile President Trump impeachment campaign who has been considering jumping into the race for months. A Steyer spokesman didn’t respond to a request for comment.

The high number of undecided voters and Feinstein’s anemic numbers could be a big motivator for Steyer and other candidates, said David McCuan, a political science professor at Sonoma State.

“She should be farther ahead,” McCuan said. “Someone outside of politics has to be encouraged to at least test the waters.”

Southern California entrepreneur Joe Sanberg has said he is also considering running.

Feinstein’s camp insisted it isn’t worried about the poll. Bill Carrick, her longtime strategist, said it was “not consistent” with other recent polls. A poll earlier this month from the Public Policy Institute of California found the race at 45 percent Feinstein to 21 percent de León, and a November poll from the University of Southern California/Los Angeles Times put it at 58 percent Feinstein to 31 percent de León among registered voters.

Carrick said de León, “a first-time candidate who’s never run statewide or even countywide,” was still a “mystery” to voters. Seventy-nine percent of respondents said they didn’t know enough about de León to form an opinion about him.

But Courtni Pugh, de León’s campaign manager, said the results were a sign of strength for the Los Angeles legislator.

“Every poll since we kicked off our campaign has seen Senator de León’s numbers rising,” Pugh said. “As Democrats are reminded of Feinstein’s record of focusing on the one percent while millions of Californians are left on the margins, the race will tighten even further. And Republicans won’t vote for her.”

Notably, 35 percent of Republicans in the poll backed de León, while 15 percent supported Feinstein and almost half said they were undecided. It’s hard to imagine them sticking with de León, a candidate who helped write California’s new “sanctuary state” bill and helped shepherd major gas tax and climate change bills through the Legislature this year — policies detested by many Republicans.

“When they find out de León is even more progressive in most of his policy positions than Feinstein, they won’t stay with him long,” DiCamillo said. Even in a top-two race with another Democrat, Feinstein would remain a strong favorite.

Feinstein, the oldest U.S. Senator in the country, has experienced unusually strong political turbulence this year, facing boos at a San Francisco event this summer when she urged patience for Trump, saying he “could be a good president” if he changed — heresy for some liberal Democrats.

Meanwhile, the poll also found two Democrats leading the governor’s race, with Lt. Governor Gavin Newsom and former Los Angeles Mayor Antonio Villaraigosa appearing to pull ahead of the rest of the candidates.

The poll put Newsom at 26 percent, Villaraigosa at 17, Republicans John Cox, a businessman, and Travis Allen, a state assemblyman, tied at 9 percent, and Democrats John Chiang, the state treasurer, and Delaine Eastin, the former superintendent of public education, tied at 5 percent, among likely voters.

If two Democrats take first and second place in the June primary — a result other recent polls have also suggested — the November general election would be the first in California history to be a Democrat vs Democrat governor’s race. And unless credible Republican candidates run for Senate, all of the top slots on the ballot could go to Democrats in November.

But 36 percent of Republicans and 22 percent of independents said they were still undecided — good news for the GOP gubernatorial hopefuls.

“It’s great to wrap up the year leading every poll, with significantly more resources, donors, endorsements, and detailed policies than all five other candidates combined,” said Newsom spokesman Dan Newman.

“While these new poll numbers are encouraging, polls don’t distract us from our goal of continuing to organize a powerful grass-roots campaign that can help Mayor Villaraigosa win the fight for greater economic opportunity,” Villaraigosa spokesman Luis Vizcaino said.

Still, Villaraigosa was the only candidate in the race to have a higher number of respondents with a negative perception of him than a positive one — 30 percent to 28 percent.

As in other polls, there was a yawning regional gap in the results, with Newsom trouncing the other candidates in the Bay Area with 55 percent and Villaraigosa leading in Los Angeles County with 31 percent. Villaraigosa also led among Latino voters with 39 percent.

The Berkeley poll, which was conducted between Dec. 7 and 16, used English- and Spanish-speaking interviewers and had a margin of error of plus or minus 3.2 percentage points.