Mayor Pete Buttigieg and former Vice President Joe Biden both face a test on Thursday, during the Democrat debates on MSNBC.

Both white male candidates currently poll in the top tier of the presidential primary, but both are struggling with racial issues.

After a black man was shot and killed by a South Bend police officer in June, Buttigieg left the campaign trail to address the black community in South Bend’s fury.

Protesters jeered at Buttigieg for failing South Bend while tending to his presidential campaign, despite the mayor marching in protest with Black Lives Matter activists and hosting a town hall meeting with the community to address the shooting.

Buttigieg’s very public response to the incident drew suspicion, however, as many black residents viewed it as damage control to protect his surging nationwide popularity.

Debate moderators will likely bring up the incident as a way to frame the challenge of police shootings in black communities.

The issue of police shootings was largely ignored during the first night of the debates, although candidates Mayor Bill de Blasio, Julian Castro, and Sen. Cory Booker spoke about the issue unprompted.

No candidate has yet used Buttigieg’s handling of the situation as a cudgel, although he continues polling above the other candidates on stage Thursday night except for Sen. Bernie Sanders and former Vice President Joe Biden.

Biden also faces questions about race after he spoke about a “more civil” time when he was able to work with Democrat segregationists who called him “son” and not “boy.”

His bipartisan successes included passing his signature 1990s-era crime bill that activists blame for unfairly targeting and incarcerating the black community.

Other uncomfortable parts of Biden’s past, including his political efforts to stop public busing surfaced as a result of his comments.

Biden has not apologized either, noting his well-intentioned efforts at the time and his long history of supporting civil rights.

Both Biden and Buttigieg face campaign debate rivals who might seize the opportunity to challenge them on racial issues.

Luckily for Biden, the 2020 candidate who led the charge demanding he apologize for his remarks about segregationists, Sen. Cory Booker, took the debate stage without singeing Biden for those remarks.

In Thursday’s debate, however, rival Sen. Kamala Harris might follow up with her earlier criticism of Biden.

“Praising and coddling individuals who made it their life work and built their reputation off of segregation of the racists in the United States. That’s a problem,” Sen. Kamala Harris said on Sunday. “I would not be a member of the United States Senate if those men that he praised had their way.”

Sen. Kirsten Gillibrand, also on tonight’s debate stage, criticize Biden’s remarks.

“We need a Democratic leader and a presidential nominee who is going to understand that the kind of language that we use around issues of race actually matter,” she said. “So it shouldn’t be that hard.”

Sen. Bernie Sanders frequently challenges Biden’s priorities while highlighting his long political record, but also called for Biden to apologize for his remarks.

“You cannot be extolling people who really were part of a disgusting system that oppressed and terrorized millions of African-Americans in this country,” he said on Sunday.

But Biden still has not apologized for his remarks, a fact that MSNBC’s Al Sharpton noted on Monday.

“I do not understand why he just can’t say, ‘This is what I was trying to say and therefore I apologize for the implication,’ and move on,” Sharpton said during an appearance on Morning Joe.

Biden’s biggest threat might be from MSNBC moderators who might use the occasion to force the apology on live television.

Lower tier candidates such as Colorado Sen. Michael Bennet, California Rep. Eric Swalwell, and Former Colorado Gov. John Hickenlooper could try to use racial issues to strike at their better polling rivals, but they might use their limited time for exposure on different issues.

Spiritual author Marianne Williamson and Andrew Yang will likely focus on getting their own brand of politics some airtime rather than striking at the racial struggles of more seasoned candidates.