Joe Biden knows the attacks will be coming. The question for the former vice president in Wednesday's Democratic presidential debate will be whether he handles them in a way that restores confidence to his anxious supporters.

With his party turning against itself on core issues, Biden will be forced to defend his record as nine eager rivals fight to knock him from his front-runner perch in the increasingly combative primary.

Biden's advisers said he expects to face pointed questions about race in particular, having stumbled in the opening debate when confronted by California Sen. Kamala Harris over his record on school integration. The pair will be joined onstage by a second senator of color, Cory Booker of New Jersey, who in recent days seized on Biden's decades-old support for criminal justice laws that disproportionately hurt minorities. The advisers said that while Biden hoped to focus on President Donald Trump, he's ready to fight back against Harris and his other Democratic opponents.

Wednesday's debate comes 24 hours after another set of 10 Democrats debated, fiercely at times, over the direction of their party. In that encounter, liberal firebrands Bernie Sanders and Elizabeth Warren faced intense criticism from lesser-known moderates who warned primary voters that a sharp shift to the left on health care and other key policies would make it all but impossible to defeat Trump.

That same dynamic will be on display Wednesday night — only in reverse.

Biden, who leads virtually all early polls, will be considered the premier moderate on stage. In addition to Harris and Booker, his more progressive opponents include New York Mayor Bill de Blasio, former Obama administration housing chief Julián Castro, Hawaii Rep. Tulsi Gabbard, New York Sen. Kirsten Gillibrand, Washington Gov. Jay Inslee and entrepreneur Andrew Yang.

While the first primary votes won't come for six more months, there is a sense of urgency for the lower-tier candidates to break out. More than half the field could be blocked from the next round of debates altogether — and possibly pushed out of the race — if they fail to reach new polling and fundraising thresholds implemented by the Democratic National Committee.

The dire stakes have forced many Democrats to turn away from Trump and turn against one another in recent weeks.

Harris landed a powerful blow against Biden in the first debate, and her polling numbers improved. She and others plan to keep the pressure on.

While the Democratic candidates agree on most things, there are subtle differences over key policies that expose the same push and pull over the direction of the party that played out Tuesday night. Immigration, trade and health care offer fertile ground for debate.

Biden, for example, has backed a plan to build off "Obamacare" and adopt universal health care for all Americans. He would allow people to keep their private insurance, while the preferred, more liberal health care alternative, known as "Medicare for All," would end private insurance and give everyone government-backed coverage.

Harris has faced criticism from all sides this week after releasing a competing plan that envisions a role for private insurance with strict government rules, but she wants to transition to a single-payer government-backed system within 10 years. In a briefing before the debate, Biden advisers indicated he would be aggressive in raising questions about the cost of Harris' health care proposal and press her to reconcile recent statements about eliminating the private health care industry.

"When it gets to health care, I think Vice President Biden might say, 'I don't know what the senator's position is,'" Biden campaign chairman Cedric Richmond said.

And with four candidates of color on stage Wednesday night, race could well be a prominent theme, though that will be dictated largely by the questions.

The debate, held in Detroit, comes two weeks after Trump used racist language to attack four Democratic congresswomen of color, calling on them to "go back" to their countries, even though all four are U.S. citizens. While the Republican president sought to distance himself from a racist chant by supporters who echoed his words at a subsequent rally, he continued to roil racial tensions over the weekend by declaring that "no human being would want to live" in a "rat-infested" part of Baltimore, which, like Detroit, is a majority-minority city.

To punctuate the point, Harris has invited black mayors from at least three different states to join the audience as her guests.

"She has to fill in the blanks. I think she wanted to run for president, but it isn't clear why," said David Axelrod, former senior adviser to President Barack Obama. "If she can fill in the 'why,' there's a play for her."

In addition to preparing to counter any new attacks on race from Harris, Biden is also readying responses to Booker, who has called the former vice president the "architect of mass incarceration" for his role in writing the 1994 crime bill that led to the imprisonment of an increasing number of minorities.

Ahead of the debate, some local Democratic organizers said they wanted to hear more from candidates about what they would do for voters in Detroit and across Michigan, particularly black voters who will be critical to a Democratic victory in 2020. That means more discussion of growing jobs and wages, housing and environmental racism.

Race didn't come up until the second hour of Tuesday's debate.

"It was really disheartening to be in one of the most populated African American cities in the country, and not have an emphasis on issues that affect black and brown communities," said Branden Synder, executive director of Detroit Action, a grassroots group that works to engage and mobilize black and Hispanic residents. "Michigan will need a federal partner when it comes to our Great Lakes, when it comes to our schools, when it comes to roads, etc., and I think that was an opportunity missed to talk to a broader state about why this person is good and how you bring back those 300,000 people to vote."

Trump won Michigan in 2016 by just 10,704 votes in an election that saw a sharp drop in turnout in areas with large minority populations.

While there is ample evidence that Democrats are paying close attention to the 2020 contest, this week's midsummer faceoff is attracting a significantly smaller audience than the first round of debates.

The Nielsen company said that just under 8.7 million people watched Tuesday's prime-time debate on CNN. That's compared to 15.3 million people who watched the first night of last month's debates.