Within minutes of taking the stage to endorse Donald Trump, boxing promoter Don King dropped the N-word at an African-American church in Ohio.
Mr King joined the campaign trail for Mr Trump alongside running-mate Mike Pence this week as part of the Republican presidential candidate's attempt to woo black voters.
Yet his keynote speaker, Mr King, failed to do much good for the campaign when he said a racial slur, shortly after claiming that black people "need" Mr Trump, who will "save the nation".
Referring to assimilation and Michael Jackson, he said: "I told Michael Jackson, I said, ‘If you're poor, you are a poor negro’ - I would use the n-word,” King said on-stage. “But if you rich, you are a rich negro.... If you're a dancing and sliding and gliding n***** - I mean negro - you are a dancing and sliding and gliding negro... So you're going to be a negro til you die."
Mr King, a Cleveland native, will join Mr Trump again this week at separate events in Dayton and Toledo.
He insisted in Cleveland Heights on Wednesday that Mr Trump was a “doctor of humanness” and would break the system.
He would restore rights for women, he added, as well as people of colour.
GOP officials including chairman Reince Preibus had reportedly convinced Mr Trump not to invite Mr King to speak at previous events.
Mr King was convicted of manslaughter after he stomped a male employee to death in 1966.
Mr Trump is polling very low among African-American voters, compared to his rival Hillary Clinton.
Yet Mr Trump said in Cleveland Heights that his polling numbers among black voters were low at first as they "didn't know what to expect", but the polls were going up "like a rocket ship" once he started to talk about the inner cities.
In August, Mr Trump started his plan to reach out to black people, saying they had "nothing else to lose".
"You're living in poverty," he said. "Your schools are no good. You have no jobs. Fifty-eight per cent of your youth is unemployed. What the hell do you have to lose?"
Mr Trump repeated the rhetoric that black voters have "nothing to lose" on Wednesday in the church.
"Some people didn't like it. But it's true. And it's amazing how it's resonated," he said.
He said he guaranteed that he would have 95 per cent of the black vote within four years.