If polls are to be believed, Sen. Dianne Feinstein is a virtual lock to finish on top in Tuesday’s 32-candidate primary.

But those same surveys might as well be looking at different contests when it comes to predicting who will grab the all-important second spot in the election and advance to the fall campaign.

“Now you’re getting into the Twilight Zone,” said Bill Carrick, a Feinstein consultant, when asked who’s likely to finish No. 2.

While state Sen. Kevin de León, D-Los Angeles, has held second place in almost every poll, his numbers have seesawed wildly.

A poll released Friday by the Institute of Governmental Studies at UC Berkeley only increased the number of question marks. Feinstein continued to hold a comfortable lead at 36 percent, with de León at 11 percent, unchanged from the group’s April poll. GOP businessman James Bradley remained in third at 7 percent, down from 10 percent.

But the numbers behind the numbers are what is really concerning for the former state Senate leader.

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“The big finding in the poll is the weakness of Kevin de León,” said Mark DiCamillo, the poll’s director. “The number of undecided voters dropped 12 percentage points,” and none of them went to de León.

More than half the voters didn’t know enough about de León to even have an opinion, which is a problem for a statewide candidate who has never run for office outside Los Angeles.

Other polls also suggest de León is far from certain to advance to the November election.

•A Public Policy Institute of California poll released last week showed de León at 17 percent, but no Republicans were included in the survey. A recent USC Dornsife/Los Angeles Times poll that did include Republicans showed de León at 7 percent.

•A SurveyUSA April canvass found de León tied for third at 6 percent with GOP businessman Rocky De La Fuente. They both trailed Feinstein at 39 percent and Republican Patrick Little, a neo-Nazi and Holocaust denier, at 18 percent.

•Then there’s a new poll done by Emerson College in Boston, which shows Feinstein at 38 percent and five other candidates, including de León, in a virtual tie for second at 4 percent to 6 percent.

That’s good news for second-tier candidates like Los Angeles Democrat Pat Harris, who has embraced the Emerson College poll because it shows him as one of the candidates in the dead heat for second.

“I feel very confident,” said Harris, an Arkansas-born attorney and animal rights activist who is running as “an unapologetic progressive.”

“The vote is going to be splintered and the second-place finisher will be lucky to get 12 percent, or maybe 10 percent,” he said.

De León’s team sees it differently.

“The polls are all over the lot,” said Jonathan Underland, a spokesman for de León. “It’s hard to put a lot of stock in what those polls are saying.”

But de León doesn’t dismiss everything the polls are showing.

“One thing we’re seeing is that Dianne Feinstein is below 50 percent in almost every poll, and that’s not good for a longtime incumbent,” Underland said.

Some of the confusion is probably linked to the large number of voters who still haven’t made a choice. The May USC/Los Angeles Times poll, for example, found that 41 percent of those surveyed were still undecided. The Berkeley poll released Friday had that number at 27 percent.

“The largest group of undecided voters are Republicans and the second-largest are ‘no political party’ voters,” said Carrick, Feinstein’s consultant. “The Democrats are with Dianne.”

That’s a problem for de León, since twice as many Republicans as Democrats remain undecided, said DiCamillo, director of the Berkeley poll. It leaves the GOP candidates with more potential voters to pick up.

“Feinstein is strong with Democrats and independents and de León can’t expect to get many votes from Republicans,” DiCamillo said. “I don’t see a constituency.”

Those undecided numbers show that Republicans and conservative-leaning independents are voters without a candidate in the Senate primary. None of the 11 GOP hopefuls is well-known, and they all lack the campaign cash to boost their visibility.

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The $12,832 that Arun Bhumitra, a Southern California businessman, had in his campaign account on May 16 was thousands more than any other Republican. And it was in a different financial universe from Feinstein’s $7 million or even de León’s $672,330.

While many of those GOP voters are going to cast their ballot for a Republican on Tuesday, there’s only an inkling of an indication they have begun to line up behind a particular candidate.

Bradley, who has shown backing in the past two polls, seems to be the only Republican within striking distance of de León, DiCamillo said.

But Bradley, a health care executive making his first run for office, has raised almost no money and may be depending on his Anglo-sounding name and businesslike ballot designation of “chief financial officer” to distinguish him from the other Republicans, DiCamillo said.

“The poll raises uncertainty,” he said.

For de León, now, it’s a matter of holding on through Tuesday.

“We’re shooting for being in the top two — that’s all we want,” said Underland, de León’s spokesman. “Because after the primary, everything changes.”

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth