Republican presidential nominee Donald Trump, left, reacts as promoter Don King catches himself using a racial slur as he introduces Trump to speak to a gathering of clergy at the New Spirit Revival Center in Cleveland Heights, Ohio, US, on Wednesday. Picture: REUTERS

BOXING promoter Don King, who was pardoned after a manslaughter conviction and has clashed with Republican Party brass, joined presidential nominee Donald Trump on an Ohio campaign swing on Wednesday.

King called Trump "an American to save the nation" at a campaign event at New Spirit Revival Centre, a largely black church in King’s hometown of Cleveland.

"He’s fearless, he’s courageous and brave and bold enough to take on the system," King said. "All things are possible with God."

Trump returned the praise.

"He is a good guy. He’s a phenomenal person. He became very rich. He’s very smart," Trump said. King’s been successful, and "I have great respect for that, and I have great respect for him."

Pence introduction

Trump’s running mate, Indiana Governor Mike Pence, introduced King.

"The party doesn’t want him, the system doesn’t want him, the lying politicians don’t want him," King said of Trump.

"We need Donald Trump, especially black people," said King, who is African-American.

The boxing hall of famer was expected to join Trump in the two other cities on the swing, Toledo and Dayton. King wasn’t expected to appear at Trump’s taping of an episode of Sean Hannity’s Fox News show on Wednesday.

Ohio is one of the most critical states to Trump’s hopes of winning the White House in the November election. Trump leads there by 2 percentage points in a four-way race in the RealClearPolitics poll average, the site said Wednesday.

RNC feud

King, who was pardoned by the governor of Ohio in 1983, clashed with Republican Party leaders in July when he said they barred him from speaking at the national convention in Cleveland where Trump accepted the nomination.

"The GOP establishment won’t control Trump, but they’re trying," said King. "I don’t think they want Trump to win."

The RNC didn’t immediately respond to a request for comment Wednesday.

Civil-rights activist and commentator Al Sharpton in February described Trump as a white version of King.

"Both of them are great self-promoters and great at just continuing to talk even if you’re not talking back at ’em," Sharpton told Politico.

Trump in June cited his endorsement from King as a defence against accusations of racism.

"Don King, and so many other African Americans who know me well and endorsed me, would not have done so if they thought I was a racist!" Trump tweeted.