CHICAGO - Barack Obama faced a potentially sticky moment on Friday when comedian Bernie Mac told a joke about “hos” at a fundraiser for him but the Democratic White House hopeful quickly told him to clean up his act.

The Chicago-born comedian and actor told what he said was a joke about his nephew coming to him and asking the difference between a hypothetical question and a realistic question.

To demonstrate the difference, he tells the nephew to go ask his mother if she would make love to the mailman for $50,000. The mother says she would make love to the mailman and anybody else for $50,000.

He tells the nephew to go ask his sister if she would make love with her neighbor for $50,000. She says she would make love with the neighbor and anybody else for $50,000.

So he tells the nephew: “Hypothetically speaking, we should have $100,000. But realistically speaking we live with two hos,” Bernie Mac said.

There was an awkward moment and nervous laughter from the crowd of about 600 people who had paid $2,300 each to attend the fundraiser at a Chicago hotel. One person objected to the word “ho” — a contraction of the word “whore” used as derogatory slang for woman — and urged Bernie Mac to leave and make way for Obama.

In his speech, the Illinois senator, who hopes to become the first black U.S. president, said unity was essential in the Democratic Party. He said it should not be divided by race, religion, region, class or gender.

“That means, by the way, Bernie, you got to clean up your act,” Obama said. “This is a family affair.”

Campaign spokeswoman Jen Psaki added: “Senator Obama told Bernie Mac that he doesn’t condone these statements and believes what was said was inappropriate.”

The comments came the day after Obama appealed to women voters to unite behind his candidacy.

Photo credit: Reuters/Mario Anzuoni (Bernie Mac smiles at the premiere of Ocean’s Thirteen at the Grauman’s Chinese theatre in Hollywood (June 2007)