DETROIT — If everything goes right for Joe Biden here, he will leave Democrats reassured.

Heading into the second heat of CNN's Democratic debates Wednesday night, the former vice president and front-runner in the polls for the 2020 Democratic presidential nomination has the chance to bolster the case for his candidacy by showing strength at a political moment that cries out for the kind of stabilizing force he's told primary voters he would be as commander in chief.

At the personal level, that means Biden demonstrating that he can punch back after absorbing body blows in the first debate. Within the Democratic Party, voters will be listening closely to hear how he makes the case that the best way to defeat President Donald Trump is with a more centrist agenda than those offered by progressive champions Sen. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, whose ideas were at the forefront of Tuesday night's first heat here.

More globally — and perhaps most crucially for Biden — is whether he can convince voters that the country is better off united, and that he can bring it together, amid the racially divisive re-election campaign President Donald Trump has been running.

"The American people know Joe Biden's qualifications and character, and tonight he's going to stress the profound stakes of this election for the American middle class, for health care, and for who we are as a people," Biden spokesman Andrew Bates said in a text message.

Biden's poll numbers have spiked in the wake of Trump's attacks on four congresswomen of color, the majority-black city of Baltimore and Rep. Elijah Cummings, the African American lawmaker whose district covers some of that city's poorest and most heavily minority neighborhoods.

While that may or may not be a sign that more Democrats are responding to Trump by flocking to Biden, a white male establishment candidate, it at least shows that the president's racist rhetoric has not been a hindrance to him so far — nor has it made voters more likely to flock to candidates of color.

From a nadir of 26 percent on July 6, Biden has rebounded to 32.2 percent in the Real Clear Politics average of national polls amid Trump's repeated racist diatribes, one of which was condemned in a House resolution that attracted only four Republican votes.

Race and related issues figure to be a focus of Wednesday's debate, in part because of Trump's recent behavior, in part because of Biden's reversal on key elements of the 1994 anti-crime law he sponsored — including his new opposition to the federal death penalty — and in part because the most fiery exchange in his last debate was with Sen. Kamala Harris of California was over his decades-old opposition to court-ordered desegregation plans involving school busing.

Sen. Cory Booker of New Jersey has hit Biden on that 1994 "crime bill," which Booker and other critics say led to an era of "mass incarceration." While changing course on elements of that law with a new criminal justice reform proposal in recent days, Biden and his allies note that prison rolls were increasing before the law was enacted.

They have also pushed back by pointing to Booker's record as mayor of Newark.

"It is Senator Booker, in fact, who has some hard questions to answer about his role in the criminal justice system,” Biden Deputy Campaign Manager Kate Bedingfield said last week. “Booker was running a police department that was such a civil rights nightmare that the U.S Department of Justice intervened.”

Biden allies say they expect him to be ready for debate-stage attacks from all sides, as Booker, Harris and Sen. Kirsten Gillibrand of New York are among the rivals who have telegraphed ways in which they may try to take down the front-runner.

Former Housing and Urban Development Secretary Julián Castro, who caught a spark in his first debate by articulating liberal views on immigration, could go after Biden on that topic — specifically the Obama administration's record of deportations and its failure to enact an overhaul to immigration laws to create a pathway to citizenship for undocumented immigrants currently in the country.

"Other candidates are searching for a breakout moment and have indicated that they plan to attack him on a host of issues, but he's not going to let anyone distort his record," Bates said.

Biden's ability to parry and jab — to hold his own on the stage — could go a long way to telegraphing to voters whether he's the Democrat best-positioned to take on Trump in a general election. His rivals are, of course, equally intent on proving that he's not.

A Harris spokesman declined to comment for this story.

Sabrina Singh, the national press secretary for Booker, said her boss would not "shy away" from "speaking truth to power" if the occasion presents itself.

For several of the candidates, it may be hard to get airtime. And for some, this could be the last opportunity to make their case to a national audience on a debate stage, because they have not yet met the donor or polling thresholds to qualify for future debates. Sen. Michael Bennet of Colorado, businessman Andrew Yang, New York Mayor Bill De Blasio, Rep. Tulsi Gabbard of Hawaii and Washington Gov. Jay Inslee are among those who will be competing to be heard.

For Biden, likely a focus of several candidates on stage, airtime is likely to be less of a challenge than making sure his performance matches his message of stability.