Donald Trump’s campaign has tried to use this week’s Republican National Convention to court African Americans by arguing that President Obama has failed them on jobs and crime. But when the GOP presidential nominee delivers his acceptance speech here Thursday, he will address an estimated 18 blacks out of 2,472 delegates.

Although that handful includes some of Trump’s most vociferous backers, the overall lack of ethnic diversity at the convention illustrates one of his greatest challenges: how to court black voters after four decades of controversy over his racial views, including campaign-trail rhetoric that has alienated many minorities.

Twelve years ago, the GOP seemed on its way toward broadening its base, boasting 167 black delegates at its convention. That year, President George W. Bush drew 16 percent of the black vote here in Ohio, unusually high for a Republican, to help secure his reelection, as well as 11 percent nationally, and party leaders had hoped to increase minority engagement in 2016.

But as Trump heads to the general election, a Washington Post-ABC News poll found Democrat Hillary Clinton leading Trump among blacks by 89 percent to 4 percent, and a recent NBC News/Wall Street Journal/Marist poll said Trump has zero support among African Americans in Ohio.

That is frustrating to the black delegates here, several of whom said in interviews that Trump has a compelling case to make to African Americans.

Speaking from the Quicken Loans Arena during the second night of the RNC, The Washington Post's Ed O'Keefe breaks down how the Republican National Convention that nominated Donald Trump for president has been more surprising - and sometimes nastier - than past conventions. (Sarah Parnass,Peter Stevenson/The Washington Post)

“The rest of America has to see the person I sat down with,” said James Evans, the chairman of the Utah Republican Party, who last month met privately with Trump after unsuccessfully trying to draft Mitt Romney to seek the nomination. “The Democratic playbook is that if you are a white Republican candidate, you are a racially insensitive candidate. Let’s look at the policies of the political left and how they devastated the black community, and you tell me who is more racist.”

Bruce LeVell, a delegate who heads Trump’s National Diversity Coalition, said he faces discrimination as a Trump supporter. “To be a black American in Georgia, and to be a Republican and to be for Trump, I can’t even tell you all the things I’ve been called,” he said.

Trump’s outlook on race has come under new scrutiny in recent days as he has stepped up his criticism of the Black Lives Matter movement, saying it is “very divisive.” He asserted that after a black man shot five white police officers in Dallas before being killed, adding, “I have seen, you know, moments of silence called for . . . this horrible human being.” The assertion came despite the fact that leaders of Black Lives Matter condemned the killing of police officers.

Trump has vowed that he would unify the races as president.

“I am not a racist,” he told The Washington Post in an interview earlier this year. “I’m the least racist person that you’ve ever interviewed.”

Trump, however, faces many challenges in winning over black voters, in part because he has been at the center of controversies regarding his racial views for decades.

The first front-page news story about Trump was a 1973 report about the federal government’s lawsuit against him and his father in a racial bias case. Trump denied discriminating against black housing applicants and settled the case without admitting guilt.

Several years later, after Trump had expanded his real estate empire by building casinos in Atlantic City, a former executive from his business accused him of making racist statements. John O’Donnell, who was president of the Trump Plaza Hotel and Casino and later wrote a memoir about his experience, said Trump blamed financial difficulties partly on African American accountants.

“I’ve got black accountants at Trump Castle and at Trump Plaza — black guys counting my money!” O’Donnell’s book quoted Trump as saying. “I hate it. The only kind of people I want counting my money are short guys that wear yarmulkes every day. Those are the kind of people I want counting my money. Nobody else. . . . Besides that, I’ve got to tell you something else. I think that the guy is lazy. And it’s probably not his fault because laziness is a trait in blacks. It really is; I believe that. It’s not anything they can control.”

O’Donnell said in an interview that he admonished Trump not to talk that way.

“You’re sitting there listening to him talk in stereotypes about black people being lazy and that it was a trait in his mind. And you just go, ‘Oh my God,’ ” O’Donnell said.

Trump told Playboy magazine that O’Donnell’s memoir was “probably true.” He told The Post earlier this year that the book was “fiction,” although he hadn’t read it. Trump said he fired O’Donnell, but O’Donnell said he quit.

In 1989, Trump inserted himself into a racially charged case in New York City. Five boys, four black and one Hispanic, ages 14 to 16, had been arrested for the brutal attack and rape of a woman who had been jogging in Central Park. Two weeks later, Trump paid for a full-page ad in four New York newspapers urging the return of the death penalty and warning of “roving bands of wild criminals.”

The jogger suffered permanent damage. The boys were convicted and served six to 13 years in prison. But years later, a career criminal confessed to the rape, providing a DNA match. The convictions were overturned, and the city paid $41 million to settle a wrongful-imprisonment suit that the men had filed. Trump called the settlement “a disgrace,” refused to apologize, and said, “These young men do not exactly have the pasts of angels.”

A few months after the Central Park incident, Trump appeared on an NBC-TV special called “Racial Attitudes and Consciousness Exam,” hosted by Bryant Gumbel. He appeared to criticize affirmative action.

“A well-educated black has a tremendous advantage over a well-educated white in terms of the job market,” Trump said on the program. “I think sometimes a black may think they don’t have an advantage or this and that. I’ve said on one occasion, even about myself, if I were starting off today, I would love to be a well-educated black, because I believe they do have an actual advantage.”

During Trump’s time as the star of his reality show, “The Apprentice,” he worked with a number of African American contestants.

Kwame Jackson, a Harvard Business School graduate who was on the first season of the show, said he saw the “Dr. Jekyll-Mr. Hyde” nature of Trump. During the taping of the show, Jackson said, Trump was respectful and Jackson didn’t think of him as racist. But when Trump became a leading voice of the “birther” movement and questioned whether Obama was born in the United States, and then spoke critically of Mexicans and Muslims, Jackson said he sadly came to a different conclusion.

“People thought he is flirting with racism, or manipulating American anger, then it became pure racism,” he said. “My distance [with Trump] grew to true disdain.”

In November, Trump drew criticism when he retweeted a tweet that said blacks killed 81 percent of white homicide victims. The claim quickly was shown to be false. The actual number was 15 percent; 82 percent of whites were killed by whites.

The number of black delegates was disclosed last month in a Republican Party email reported by Post columnist Jonathan Capehart. A party official did not respond this week to a request for comment.

Trump declined an invitation to speak to the NAACP’s annual convention, which was held in Cincinnati this week. The civil rights organization said Trump’s campaign cited a scheduling conflict with the Republican convention.

Although only a handful of African American delegates are at this week’s convention, a number of blacks have been given prominent speaking roles, On Monday night, Milwaukee County Sheriff David Clarke Jr., who has called Black Lives Matter a “hate group,” praised Trump as “the steadfast leader our nation needs.”

Trump, meanwhile, said in the interview earlier this year that his candidacy would be best for African Americans.

“Somebody said Make America Great Again is a very negative theme,” he said. “I said, ‘No, it’s a very positive theme because people have been disenfranchised.’ Look at African Americans. I mean, I’m going to be so great. I think I’m going to do great with African Americans.”