Los Angeles(CNN) In yet another sign of trouble for Sen. Kamala Harris in the 2020 presidential race, the California Democrat has slid from an enviable front-runner position in her home state into the single digits in a new poll of likely voters in the Golden State.

As the state's March 5 primary draws closer, Sen. Elizabeth Warren of Massachusetts (23%), former Vice President Joe Biden (22%) and Sen. Bernie Sanders of Vermont (21%) are now tied as the leaders in the field among likely voters who are either registered as Democrats or identify as Democratic-leaning independents in the new Public Policy Institute of California poll, which was conducted in mid- to late September after Harris' uneven performance in the last debate.

Harris tumbled from 19% in July to 8% in the new poll by the institute, failing to sustain the momentum she sparked with her first debate performance in June. She lost significant ground over the summer, while her chief rivals all solidified their standing among California voters.

In the July poll, Warren was at 15%, Sanders was at 12% and Biden was at 11% -- all trailing Harris, who got both a fundraising and a polling bounce after she delivered a fiery performance in the first debate in Miami by questioning the former vice president's past opposition to busing for the purpose of desegregating schools.

While it is often said that California tends to reflect the national state of play of the presidential race -- because it is so expensive to wage an intensive campaign in this vast and diverse state -- the new Public Policy Institute of California poll underscores that Harris does not seem to be drawing any advantage from the fact that she served as the state's attorney general and continues to serve constituents as the state's junior US senator.

"These numbers reflect what's going on in the national scene, but they also reflect that there is not a home state advantage (for Harris). There's not an advantage from the fact that she's run in statewide races here in 2010, 2014 and 2016," said Mark Baldassare, who directs the survey and is the institute's president and CEO.

Harris' supporters and advisers had hoped she would be able to rack up a considerable number of delegates in California when the state holds its Super Tuesday contest, building momentum that would carry her into the spring primaries.

"Sen. Harris has to prove to (California) voters just like any other Democratic presidential candidate -- 'What are you going to do for me?' and 'Where do you stand on the issues?' and 'Are you the person who is most likely to defeat Donald Trump?'" Baldassare said. "The name identification associated with being the state's senator and somebody who's been on the ballot -- it's not an advantage right now."

The new California poll numbers come as Harris' campaign is restructuring its leadership and attempting to streamline its decision-making. After stumbling through a fog of confusion about her position on the single-payer "Medicare for All" proposal and amid falling poll numbers over the past three months -- including in South Carolina, where a recent survey showed her at 3% -- Harris is moving her Senate chief of staff, Rohini Kosoglu, and senior adviser Laphonza Butler into top leadership positions within the campaign.

Harris -- who has notched a series of firsts in her career, including becoming California's first female attorney general of color -- has acknowledged at campaign events that she faces some unique hurdles; namely, as she likes to point out, that Americans have never elected a president who looks her.

But she has vowed to soldier on. During a recent fundraiser in Los Angeles, she laughed when retelling the story of how a reporter recently overheard her telling fellow Sen. Mazie Hirono of Hawaii, "I'm f*****g moving to Iowa," which will hold its first-in-the-nation caucuses on February 3. That comment was heard far and wide, and Harris noted to laughter that the famed Des Moines T-shirt company RAYGUN is printing her remark on one of its shirts.

As they strategize for the Golden State primary, Harris and all of the other Democratic candidates will have to contend with a darkening mood among California voters they see signs of weakness in the US economy and grapple with a homelessness crisis statewide.

Homelessness ranked as the most important issue facing the state for the first time in the Public Policy Institute of California survey's 20-year history, according to Baldassare. That was followed by voters' concerns about jobs and the economy, as well as rising housing costs -- which have contributed to increasing numbers of Californians living on the streets.

Baldassare noted that homelessness moving to the top of the list of concerns was an astonishing finding.

"It's just incredible," Baldassare said. "It's visible, and it's a growing issue. ... It's a very tough issue. It's disturbing for people to see the suffering that's occurring -- it's something that doesn't fit with their image of what should be going on in their community. And they're frustrated that the government seems incapable of getting its hands around it. It's not just a San Francisco or an LA issue anymore. It's everywhere."

Signs of economic uncertainty are also weighing on California voters. A year ago, 53% of Californians said they expected to see good economic times over the following 12 months. Now only 41% of the state's residents said they expected good times over the next year, while 50% said they expect bad times financially.

"More people are getting nervous about the direction of the economy," Baldassare said. "That's a big change. That speaks to some combination of political and economic uncertainty really surfacing -- and that has impacts on what choices people make when they go to the ballot. They tend to feel more negative about incumbents and officeholders, because they feel like, 'Why aren't they doing something about this?' They're going to be looking for some message of hope or a plan for what they're going to do if things get worse."

The Public Policy Institute of California survey was conducted via telephone from September 16 to 25 with 1,705 California adult residents. The results have a +/- 3.2 percentage point sampling margin of error for all adults, a +/-3.7 percentage point sampling margin of error for 1,344 registered voters and a +/- 4.2 percentage point sampling margin of error for 1,031 likely voters.