'What do you have to lose?'

Donald Trump made a sustained pitch Friday to African American voters, who have overwhelmingly flocked to his Democratic rival Hillary Clinton, telling them: "what do you have to lose?"

The Republican presidential nominee, who languishes in the polls both nationwide and in virtually every battleground state, faces an uphill battle to broaden his support base if he is to avoid a Democratic landslide in November.

"No group in America has been more harmed by Hillary Clinton's policies than African Americans," Trump told a rally in Dimondale, Michigan.

"If Hillary Clinton's goal was to inflict pain on the African American community, she could not have done a better job. It's a disgrace," he added.

He told the crowd that he was asking for the vote of "every single African American citizen in this country who wants to see a better future."

"Look how much African American communities have suffered under Democratic control. To those I say the following: what do you have to lose by trying something new like Trump?" he said.

The New York billionaire, whose controversial run for the presidency has attracted white supremacists, alienated immigrants and done little to win over minorities, said blacks were living in poverty facing disproportionately high unemployment rates and without good schools.

"Your schools are no good, you're living in poverty... What the hell do you have to lose?" Trump repeated.

African Americans voted overwhelmingly in favor of outgoing Democratic President Barack Obama and Clinton's husband, former president Bill Clinton.

In 2012, Republican nominee Mitt Romney won only six percent of the black vote.

Trump also sought to reboot his flagging presidential bid, dismissing his tainted campaign chairman.

The resignation of the seasoned Republican strategist Paul Manafort -- under fire for his pro-Kremlin ties and role in a Ukrainian corruption scandal -- represents the Republican nominee's latest effort to get back on track after weeks of crisis.

Trump shocked many on Thursday by expressing "regret" for past mistakes, and began airing his first television ads on Friday in a desperate attempt to chip into Democratic rival Hillary Clinton's yawning lead in the polls.

Clinton now leads 47.2 percent to Trump's 41.2 percent among Americans, according to an average of national polls from Real Clear Politics, and is ahead in virtually every swing state.