ATLANTA (AP) -- Barack Obama called Sunday for unity to overcome the country's problems and acknowledged that ""none of our hands are clean"" when it comes to healing divisions. Hillary Rodham Clinton picked up a Harlem church leader's endorsement.

Heading into the most racially diverse contest yet in the presidential campaign, Obama took to the pulpit at Martin Luther King Jr.'s Ebenezer Baptist Church on the eve of the federal holiday marking the civil rights hero's birth 79 years ago. He based his speech on King's quote that ""Unity is the great need of the hour.""
""The divisions, the stereotypes, the scapegoating, the ease with which we blame the plight of ourselves on others, all of that distracts us from the common challenges we face: war and poverty; inequality and injustice,"" Obama said. ""We can no longer afford to build ourselves up by tearing each other down. We can no longer afford to traffic in lies or fear or hate. It is the poison that we must purge from our politics; the wall that we must tear down before the hour grows too late.""
In New York, Clinton told how she had traveled years ago with her church youth group to hear his speak.
""It was a transforming experience for me,"" Clinton said. ""He made it very clear that the civil rights movement was about economic justice.""
A day earlier, Clinton defeated Obama in Nevada's caucuses and the two challengers are looking ahead to South Carolina, where the Democratic primary is Saturday. The state is the first where a large number of black voters will participate, and Obama needs a win to remain a front-runner in the race for the party's presidential nomination. He won the leadoff contest in Iowa, and lost New Hampshire and Nevada to Clinton.
Obama is counting on blacks to stick with him despite his losing two in a row to Clinton. He lost Nevada despite winning 83 percent of blacks, who made up 15 percent of the total vote. In South Carolina, they are expected to make up at least half the turnout.
Obama's campaign has worked to overcome concerns among black voters that he wouldn't be able to win an election in white America. But his poll numbers leaped among blacks after his victory in practically all-white Iowa.
""I understand that many of you are still a little skeptical,"" Obama said Friday night at a King banquet in Las Vegas. ""But not as skeptical as you were before Iowa. Sometimes it takes other folks before we believe ourselves.""
He said in an interview with the Rev. Jesse Jackson on WVON-AM in Chicago that South Carolina is ""absolutely critical to our success.""
After appearing in Harlem, Clinton picked up the endorsement of the Rev. Calvin Butts. As dozens of Obama supporters shouted ""Harlem for Obama,"" Clinton's supporters tried to drown them out by shouting ""Hil-la-ry!""
Clinton spoke warmly of her opponent saying, ""I recognize what a challenging choice this is.""