If you thought Tuesday night’s Democratic debate was combative, just wait for the rematch between Joe Biden and Kamala Harris.

The former vice president has maintained his primary front-runner status and ridden out a dip in the polls since their debut battle last month in Miami. But Biden was widely seen as faltering in the face of the California senator's carefully planned attacks last month -- raising questions about his political readiness for what is sure to be a grueling campaign.

He's not likely to let such attacks slide Tuesday night. “I’m not going to be as polite this time,” Biden told supporters at a recent fundraiser.

But Biden could be facing even more trouble on stage Wednesday night, the second of two back-to-back debates in Detroit. The former vice president will be flanked by two of his most vocal 2020 rivals – Harris and Sen. Cory Booker of New Jersey.

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Booker has increasingly sought to take on Biden, apparently in a bid to replicate Harris' success in gaining momentum by attacking the front-runner. And Harris has shown little signs of letting up either.

In the defining moment of the first round of debates, Harris cold-cocked Biden as she criticized comments by the former vice president spotlighting his ability to find common ground during the 1970s with segregationist senators with whom he disagreed, and over his opposition decades ago to federally mandated school busing.

The fallout from the Miami showdown was almost instant. Biden saw his once large lead in national and early voting state polling deteriorate – while Harris soared in the surveys.

Biden told reporters last week that he "was probably overly polite in the way I did respond to an attack" in the first debate.

And a source close to Biden’s inner circle told Fox News that the former vice president is prepared and “plans on being a little feistier.”

“I think he knows that he’s not in the vice president’s office anymore and he’s on the campaign trail and has to conduct himself accordingly,” added the adviser, who asked to remain anonymous to speak more freely.

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Biden’s numbers have rebounded in recent national polls by Fox News and Quinnipiac University. But Mo Elleithee, the founding executive director of Georgetown University's Institute of Politics and Public Service and a Fox News contributor, emphasized that the former vice president still has a lot on the line in tonight’s debate.

“Biden needs to rebound. Biden needs to show people that last time was a fluke,” he said. “His challenge is going to be a lot of people saw last time that he was vulnerable. A lot of people saw him get knocked off the horse. And so I would suspect people will be doing that this time.”

Elleithee, a senior spokesman for Hillary Clinton’s 2008 presidential campaign who later served as communications director for the Democratic National Committee, said that Biden’s mission is “to show that he will not get knocked off the horse and that he does have that he has that strength he was projecting early in his campaign.”

Biden’s turned up the volume on the criticism of his 2020 Democratic White House rivals – taking swipes at Booker's record as Newark mayor, and questioning Harris over her truthfulness on how she’ll pay for her "Medicare-for-all" proposal.

Hours before Wednesday night’s debate, senior Biden campaign officials emphasized “we have to be prepared for mischaracterizations. I think tonight we may see some flat out lies and distortions about his record.”

They highlighted that Biden will “make a strong case” for his recently released health care proposal “and draw contrasts with the plans of his opponents.”

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Biden – who’s the only one of the top contenders who opposes the plan, in which all Americans would obtain their health insurance from a government-operated program like Medicare – is calling for reinforcing the Affordable Care Act (better known as ObamaCare) by adding a public option.

“I don’t expect him to come out of the gate directly criticizing in any personal way Sen. Harris, but he’s certainly going to draw a contrast about the plan that she’s put forward versus his,” senior campaign officials said.

And they noted that Biden will likely also shine a light on his criminal justice reform plan, which he unveiled last week. His wide-ranging plan to reduce the country’s prison population, reform the nation’s criminal justice system and eliminate racial and income disparities in sentencing would reverse the stricter sentence terms for crack versus powder cocaine implemented by the now-controversial 1994 crime law that then-Sen. Biden helped craft.

Booker quickly slammed Biden for being “the proud architect of a failed system" and argued that the crime bill “put mass incarceration on steroids and so I'm disappointed that it's taken him so long to own up to that.”

But Biden punched back at Booker's claim that he was the mass incarceration "architect," telling reporters recently that "Cory knows that's not true."

The former vice president criticized the stopping and frisking of black men by Newark police during Booker's tenure as the city's mayor. He added that during his years as vice president, "the Justice Department took action against them, held the police department accountable. He (Booker) objected to federal interference."

The Biden campaign called Booker’s attacks “a mischaracterization not only of the Vice President’s record but he went directly to his character.”

“Cory’s plan is to go out there and be himself,” a senior Booker campaign official told Fox News regarding Wednesday's debate.

“That involves sharing his positive vision of bringing people together to defeat Donald Trump. But he’s also not going to hesitate to speak truth to power if that’s what the debate demands. That’s what he did last week when he critiqued Biden’s plan,” the official said.

The Harris campaign stayed mum regarding the former California attorney general’s debate strategy.

But Elleithee emphasized that “she needs to establish that the first debate wasn’t a fluke. She needs to show that she can command a debate stage consistently. I think she is well-positioned to do that.”

“She’s proven that she knows how to do this.” But he noted that “history is full of candidates who had one good debate and then faded away. This is her opportunity to show people that she can do this consistently.”

It’s not just Booker and Harris who may throw punches at the front-runner. It’s also in the best interests of longer-shots Sen. Michael Bennet of Colorado, Gov. Jay Inslee of Washington state, and former Housing and Urban Development Secretary Julian Castro to see the former vice president’s aura of electability weakened.

Ditto for Sen. Kirsten Gillibrand of New York, Rep. Tulsi Gabbard of Hawaii, and New York City Mayor Bill de Blasio, who are also on the stage tonight. They along with Inslee, Castro and Bennet are all not guaranteed a place in September’s third round of primary debates – thanks to the raising of the qualifying thresholds by the Democratic National Committee.

Bennet told reporters on Tuesday morning that “part of the vice president’s argument has been that the problem we’re facing is Donald Trump and that if we just got rid of Donald Trump, everything would kind of go back to normal when he was making bipartisan deals in the Senate.”

Sharpening his knives, Bennet took aim at Biden for his years in the Obama administration.

“It is an absolute misunderstanding, a miscomprehension, of where we are as a country right now to imagine that if just get rid of Trump it will all go back to normal. The reason Trump is there in part is that we were a mess before he got there,” he argued. “People said ‘look, we can’t do any worse than this. We might as well put a reality TV star in charge to blow the place up.’”