The former New York mayor Michael Bloomberg has made a huge push in recent weeks to attract black voters to his ground-breaking campaign to win the Democratic nomination for president.

As he has poured more than half a billion dollars so far into creating the richest nomination campaign in US history, he has ploughed huge efforts into trying to win over one of the most vital parts of the Democratic electorate: black voters.

In recent days Bloomberg has rolled out a bevy of endorsements, including from Congressional Black Caucus members who have previously criticized some of his policies and prominent African Americans in the legislature in South Carolina, which is the vital next state to vote.

He has used paid media to target African American communities and has participated in events in parts of the country that are key for Democratic African American turnout – like the Alabama Democratic Conference or Detroit’s Greenwood Initiative.

Bloomberg’s campaign has opened field offices in states where African Americans make up significant portions of the Democratic vote – Georgia, Alabama and North Carolina.

But all that huge effort may have come into jeopardy with a nationally televised pile-on by his rivals in the primary debate last week that focused on his controversial “stop-and-frisk” policing strategy as mayor that unfairly targeted blacks and Hispanics.

“[It was] devastating. I don’t think there’s anyone with the history of Michael Bloomberg that people can actually say he’s better for black folk than any other candidate,” said Bakari Sellers. “I think beyond Pete [Buttigieg], Amy [Klobuchar], he’s probably last to that specific issue. But black folk are looking for somebody who can beat Donald Trump and last night he failed that test royally.”

For Bloomberg wooing black Americans might represent the single biggest challenge to his astonishing campaign that has already spent over $500m to create a national bid for the White House by hiring thousands of staffers and flooding the airwaves and social media with expensive political ads.

Facebook Twitter Pinterest People pray before a speech by Mike Bloomberg at the Buffalo Soldiers National Museum in Houston, Texas. ‘I do think that there’s a lot of skepticism of what he will produce for black communities,’ said Alicia Garza, co-founder of Black to the Future Action Fund. Photograph: Callaghan O’Hare/Getty Images

It has bought him a place on the debate stage, forced his way into polls and leapfrogged many poorer rivals to become a top-tier candidate. But even with all that there remains both skepticism and curiosity among the black community about Bloomberg and his campaign, said Alicia Garza, the co-founder of the Black to the Future Action Fund.

“I do think that there’s a lot of skepticism of what he will produce for black communities,” Garza said. “Certainly there are people and black leaders who have gotten behind him. What we know about black voters is that we’re practical. If we’re looking at a framework of can Bloomberg beat Trump I think there are black voters out there who say, ‘yeah, we can.’ But I think when we start to look at his policies and his record in relationship to black communities it’s a pretty mixed bag.”

Garza added: “There are certainly concerns about his record with stop-and-frisk. There are certainly concerns about some comments that he’s made about African Americans and Latinos and who will hire us? He’s made a lot of comments about women and trans people and I do think that that concerns voters, especially black voters.”

Democrats of all backgrounds this cycle really want a candidate who can beat Trump. That remains one of the main priorities of Democratic voters.

“The interesting thing about this election – it has bordered on one concept: can you beat Trump? Can you beat Trump? Nobody is talking about in terms of race. Nobody’s talking about it in terms of gender. The big question is ‘can you beat Trump?’” said veteran Democratic strategist Minyon Moore.

In the last two Quinnipiac University national polls Bloomberg’s approval ratings among African American voters have jumped from 7% in January to 22% in February

Bloomberg, like former vice-president Joe Biden, has styled his presidential bid around the argument that he’s best equipped to beat President Trump. And in the months since Bloomberg has entered the Democratic primary, his approval numbers among African Americans have grown.

“There is this real sentiment within the black community that is both broadly felt and intense – the need to get rid of” Trump, said Adrienne Shropshire, the executive director of the African American organizing group BlackPac. “People who are without a doubt looking for someone who can do that. People believe that Trump is going to cheat … and they believe that Bloomberg can counter that, that Bloomberg has more money than [Trump] does. There is this sort of two New Yorkers thing that Bloomberg, because he’s a New Yorker, he knows how to fight him, that he’ll use whatever tactics he needs to win.”

In the last two Quinnipiac University national polls Bloomberg’s approval ratings among African American voters have jumped from 7% in January to 22% in February.

But Bloomberg is hardly a lock for support among black voters. Biden still polls competitively among black voters in South Carolina, a state with a large Democratic African American community that candidates covet.

But there are also black voters who remain skeptical of Bloomberg. Sellers said Bloomberg is effectively trying to buy his way into the election despite tone-deaf policies.

“I call what he’s doing an attempt to economically persuade individuals to support his campaign,” Sellers said.

Facebook Twitter Pinterest ‘The interesting thing about this election – it has bordered on one concept: can you beat Trump? Can you beat Trump?’ Photograph: Callaghan O’Hare/Getty Images

Still, Bloomberg’s viability has seeped into the American political debate. During a recent episode of the podcast Lovett or Leave It, comedian Larry Wilmore went on a riff about the motivations of Africans Americans who support Bloomberg.

“I think black people want a winner more than anyone else. That’s why the whole Bloomberg thing’s confusing. White people who want black people to react to racism exactly how they react to racism – it’s like ‘how can you vote Bloomberg?’ Because that motherfucker’s got some bling and can win,” Wilmore said in the podcast episode, chuckling before becoming more serious. “That’s how they’re reacting to it”

The black vote is regarded as crucial for any successful Democratic presidential candidate.

In 1976 the then Georgia governor, Jimmy Carter, won the Democratic nomination with strong support among black voters in the south. Four years later when Senator Ted Kennedy ran, the coalition Carter had built among the African American community helped him stave off Kennedy’s challenge and win his party’s nomination. In 1988 support by southern African Americans helped Jesse Jackson win a swath of key southern states and propelled him to be the runner-up in the Democratic primary, behind Governor Michael Dukakis.

More recently, Bill Clinton and Barack Obama catapulted over rivals to their party’s nomination and eventually the presidency thanks to support from black voters.

Strong black support for Bloomberg in particular is also key to his strategy. He has skipped the first four early primary states to concentrate on the set of “Super Tuesday” contests in March. A few of the southern Super Tuesday states have large and essential blocs of African American voters.

Even before Bloomberg qualified for the debate, he had been doing practice sessions with his team. Some of the attacks were obvious: he would have to explain his stop-and-frisk policies as mayor. He would have to explain calling the signature healthcare law of the first black president “a disgrace”. He would also have explain past comments he made saying getting rid of a discriminatory housing law was the reason for the 2008 mortgage crisis.

All of those topics came up in the debate in Nevada last week and Bloomberg’s opponents landed blows on the mayor.

“Democrats are not going to win if we have a nominee who has a history of hiding his tax returns, of harassing women, and of supporting racist policies like redlining and stop-and-frisk,” Warren said at one point during the debate, referring to Bloomberg. “Look, I’ll support whoever the Democratic nominee is. But understand this: Democrats take a huge risk if we just substitute one arrogant billionaire for another.”

With all that though, South Carolina really serves as the first indicator of major black support within the Democratic party. Arisha Hatch the vice-president and chief of campaigns for the progressive not-for-profit Color of Change said support hasn’t coalesced around one candidate.

“I think black voters, for the most part, are very much undecided in this primary election,” said Hatch.

Hatch added: “The next couple of weeks are going to be very telling.”