Democratic candidates Hillary Clinton and Bernie Sanders clashed over support for the American president in their first debate since the New Hampshire primary.
Mrs Clinton sought to cast herself as the protector of Mr Barack Obama’s legacy, sharply attacking Mr Sanders for criticising the president.
“The kind of criticism I hear from Senator Sanders, I expect from Republicans,” Mrs Clinton said.
At the PBS NewsHour televised debate, Mrs Clinton repeatedly emphasised her ties to Mr Obama, who is extremely popular among minority voters.
Meanwhile, Mr Sanders took pains to tailor to his message of economic fairness to address disparities in black communities.
Mrs Clinton also stressed her pragmatism, questioning Mr Sanders’ pledges to provide universal health care and free higher education.
“We have a special obligation to make clear what we stand for, which is why we can’t make promises we can’t keep,” Mrs Clinton said.
Immigration reform was also a major topic of discussion.
Both candidates supported creating a path to citizenship for the nearly 11 million undocumented immigrants in the US and they decried a recent uptick in deportations by the Obama administration.
Criticising the anti-immigrant positions of Republican front-runner Donald Trump, Mr Sanders said immigrants should not be scapegoats for economic uncertainty.
“We have got to stand up to the Trumps of the world, who are trying to divide us,” Mr Sanders said.
Borrowing language from her opponent, Mrs Clinton said the economy was “rigged” in favour of the rich.
Mr Sanders took aim at mass incarceration, promising if elected the US would no longer have the largest prison population in the world.
Mrs Clinton contended that Mr Sanders’ sweeping proposals would increase the size of the government by 40 per cent.
Mr Sanders spoke more authoritatively on foreign policy, a weakness in earlier debates.
Asked to name a foreign leader they admired, Mr Sanders pointed to Winston Churchill while Mrs Clinton selected Nelson Mandela.
Mrs Clinton is trying to rebuild her campaign after Mr Sanders decisively won the New Hampshire primary.
She received a much-needed endorsement from an influential bloc of black Democrats in Congress on Thursday.
The Vermont senator won the New Hampshire primary by 22 percentage points and lost the Iowa caucuses narrowly, but both states have nearly all-white populations.
He now faces the challenge of finding votes among the sizable Latino and black electorates in Nevada and South Carolina.
But the former secretary of state has strong support among Latinos and African-Americans and is expected to do well in the two states.
Recognising the need to do more to court the black vote, Mr Sanders met the civil rights leader, the Reverend Al Sharpton, in New York on Wednesday.
However, the Rev Sharpton declined to say which candidate he would back after the meeting.