Democratic candidate Joe Biden is expected to win the second round of presidential debates on Wednesday after the first night revealed divisions between the party´s centrist and progressive wings.
Biden, the former vice-president who is ahead of his rivals in the race to defeat Donald Trump next year, is expected to be full of energy and ready for battle after a lukewarm performance in a debate last month.
Biden, 76, is competing in Detroit with Senator Kamala Harris and Senator Corey Booker, the two black candidates who are likely to focus on controversial issues during his 36-year political career.
It is expected to shed light on Biden´s record on crime and racism, a question that has overshadowed Washington after Trump´s continuing attacks on minority Democrats.
Biden, whom Trump described as Joe the Nessim, appeared unprepared when Harris attacked him in June over his decades-old relationship with members of Congress who called for apartheid.
"I will not be polite this time," Biden said at a fund-raiser last week.
Twenty candidates will participate in the debate during two nights in Michigan, which Trump can win in 2016.
US senators Bernie Sanders and Elizabeth Warren faced violent attacks from their moderate opponents during a debate on Tuesday between Democratic candidates for the presidential race in the 2020 election and revealed lines of ideological division within the party.
This round of debates is very important for the large number of candidates, who are likely to fall by half before the next debate in September.
Warren and Sanders, who are equal in opinion polls, have a similar political agenda. Both support health care for all Americans, making education in government colleges free, increasing taxes on the rich and more stringent regulation of the money market.
Warren and Sander resisted attacks during the two-and-a-half-hour debate, dealing with everything from jobs and foreign policy to arms and tax violence, and how long the president should be.
"I do not care how old you are, what I care about is your vision," said 37-year-old Pete Botejaj, 77, of Sanderz.
But while Sanders called for a "political revolution," former Colorado Governor John Hickenloper warned of the cancellation of private health insurance for hundreds of millions of people.
Expanding health care should be "progress, not revolution," he said.
There have also been divisions among candidates on immigration and trade.
Warren´s plan not to criminalize the passage of illegal immigrants into US territory was met with a harsh response from the governor of Montana, Steve Bullock.
"A logical immigration system needs a rational leader, and we can do it without resorting to dropping prosecutions," Pollock said.
"I do not understand why it costs a lot of trouble for someone to compete for the post of president of the United States to talk about what we can not do and what we should not fight for," she said, applauding the audience.
