(CNN) - With her poll numbers hitting a stubborn plateau, the third Democratic presidential debate may become a key moment for Sen. Kamala Harris to recapture the momentum her candidacy has lost in recent weeks, multiple sources inside and outside the campaign said.
"This is a crucial month for her in fundraising and debates," one Harris adviser said. "The campaign can't survive on glimpses and glimmers.
"If she doesn't do well, it's harder to reverse the shift," the source added.
Harris' team hopes to surface a different side of the California senator and former prosecutor: one that emphasizes aspects of her personality that are more often seen in unscripted moments on the campaign trail than in Harris' biggest televised moments on the national stage, according to multiple campaign aides.
The objective: defend Harris' record while also appearing presidential by staying above the fray and avoiding messy fights on the stage. Aides want Harris to continue opening up about her personal experiences, channeling interactions with voters where her aides believe she has most shined on the campaign trail -- and countering a perception that she is overly rehearsed and planned.
Harris' toughness and ability to "prosecute" a case against a second term for President Donald Trump has been the centerpiece of her appeal to voters.
Whether it is Harris' questioning of Trump administration officials or Supreme Court Justice Brett Kavanaugh during congressional testimony, the campaign has been eager to embrace Harris' persona as a candidate who is "tough" enough for a general election fight against Trump.
But at Thursday's primary debate, her campaign hopes she will lean into an earlier theme in her campaign -- being a "joyful warrior," according to a source with direct knowledge of the strategy.
"Her entire tagline as being a joyful warrior is something that people respond to really well on the campaign trail, and that's something they want people to see on the debate as well," that aide said.
For Harris, the terrain of the primary race has suddenly threatened to morph into quicksand. Her poll numbers have stagnated in the mid-single digits after her spike following the June debate. When CNN released an August poll that showed Harris had fallen back down to 5% nationally, a Harris campaign adviser described it as "the lowest point of the campaign thus far.
"I think sometimes she feels like she's putting a guard up. Like it's more of a show, you know what I mean?" Yamaisi Errasti, a 22-year old University of South Carolina Graduate student who is still an undecided voter, told CNN. "It's just trying to pursue or portray a certain image of herself, as opposed to her authentic self."
Ian Sams, Harris's national press secretary, said the senator's focus in this debate will be on pitching herself as a "unifying" candidate.
"Kamala will take on Donald Trump directly and will focus on bringing the country together by defeating him and unifying Americans around solutions to our common challenges," Sams said. "She'll make the connection between his hatred and division and our inability to get things done for the country."
Her campaign is also seeking to confront a challenge that Harris uniquely faces as a black woman running for president: rounding out her image as both competent and presidential, while also revealing more of her personal side.
"It's a black woman running for president of the United States," said Bakari Sellers, a Harris surrogate and CNN political commentator. "And I think the bar is going to be higher, and she has to be able to reach that, and I'm sure she will.
"So I think a lot of it is just navigating that," he added.
Still, some Harris aides downplayed the significance of this debate for her, arguing that voters are just beginning to pay attention to the race, and there is still time for Harris to capture their attention.
"We're now in the part of the race where voters start kicking the tires," one campaign senior official said. "We're now getting into the meat of the campaign."
June's debate provided Harris the high point of her campaign. Harris took Joe Biden to task for his remarks about two segregationist senators, in which he cited them as examples of colleagues he could work with during an era where "at least there was some civility" in the Senate. Harris called the words "hurtful," then recalled how, as a child, she was bused to school in a local effort to desegregate districts.
"That little girl was me," she told Biden.
The attack proved effective in getting the attention of some Democratic voters, but campaign aides, advisers and donors say that the aftermath has been complex. She experienced a bump in both polls and fundraising afterward.
But one Harris fundraiser complained that the attack backfired because it now looks more like a premeditated ambush with the campaign even printing T-shirts with Harris' line "that little girl was me." The T-shirt and preparation felt "staged" and "prosecutorial," more like a courtroom act, the fundraiser said.
The days following Harris' performance were inconsistent. She struggled to clearly explain whether she would support federally mandated busing in current times when pressed by reporters, prompting a heated back and forth between Biden, Harris and their surrogates over whether Harris and Biden actually agree on the very issue she used to attack the former vice president.
Aides described Harris's second debate performance in July as a wash -- it was neither disastrous for her candidacy nor was it particularly helpful.
But the most damaging moment came when Rep. Tulsi Gabbard levied an attack, that many of Harris' allies described as predictable, on Harris' prosecutor record.
Gabbard attacked Harris' record as California attorney general, in a string of accusations, some of which were later deemed by fact checkers to be false and misleading. Even though the campaign saw the Gabbard attack coming, Harris failed to effectively halt or avert it.
Aides acknowledged that Harris was not prepared and didn't effectively shut down the attacks on the stage.
In rolling out her criminal justice plan this week, the campaign wants the senator to be able to defend her record and refocus the criticism Harris faced on her plan to reform the system. Harris has also faced more questions about the very critiques levied at her by Gabbard and criminal justice reform activists, especially in the area of legalizing marijuana and the disproportionate rate of people of color who are convicted.
"Emotionally, it's hurtful," she told the New York Times about the criticism coming from young black activists.
Taken together, the two moments -- Harris's moment with Biden and the exchange with Gabbard -- portrayed Harris as eager to go on the attack on other candidates' records but unable to defend her own.
This time, however, there will be less of a focus of pitting Harris against any of the other candidates on the stage, and far more focus on painting a clearer picture for voters of who she is.
"I would want to see more about her personality," said Ivon Garcia, of Rockville, Maryland, told CNN. "I personally don't know much about Harris right now."
Aides are watching for other dynamics on the stage, as well. They're zeroing in on how Biden and Massachusetts, Sen. Elizabeth Warren interact and if Warren becomes a bigger target from the field, given her rise in the polls. Harris insiders say Warren is increasingly viewed as the candidate who poses the biggest concern to Harris because her support has continued to grow at a gradual, but constant rate.
"That suggests Warren's support is far less likely to collapse," a Harris campaign adviser said.