MONTGOMERY, Ala. — The president of the Southern Poverty Law Center told staff members on Friday that he would step down from the crusading civil rights nonprofit, which has been roiled by charges of racism and sexual harassment and ousted its co-founder last week.

Richard Cohen, the president of the S.P.L.C. since 2003, cited “recent events” in an email to staff members on Friday, writing that he had asked the center’s board to open a search for an interim president “in order to give the organization the best chance to heal.”

“Whatever problems exist at the S.P.L.C. happened on my watch, so I take responsibility for them,” Mr. Cohen wrote.

Mr. Cohen’s leadership of the center, one of the nation’s wealthiest and best known nonprofit groups, has been under siege in recent weeks.