The final days of the historic Chicago mayor’s race between two black women have turned so acrimonious that the Rev. Jesse Jackson has called for reconciliation between the two candidates the day after the election.

“I just don’t want it to get too out hand,” said Mr. Jackson, a two-time presidential candidate and elder statesman among the city’s African-American community. “Tuesday, the race will be over and the healing must begin.”

Both former federal prosecutor Lori Lightfoot and Cook County Board President Toni Preckwinkle signed a pledge to meet on Wednesday even as they were attacking one another over the weekend. The winner of the nonpartisan runoff will be the first black woman to lead the nation’s third largest city.

Ms. Lightfoot is far ahead in polls and the gap has prompted Ms. Preckwinkle and her allies to ratchet up their attacks. Each woman is fighting hard to win over the African-American community, which accounts for about a third of the city’s population.

One ad airing over the weekend criticizes Ms. Lightfoot, who led a board charged with overseeing the Chicago police, for being unsympathetic to African-Americans abused by police officers. Similar attacks have prompted a series of heated exchanges during debates, including charges by the candidates that the other is lying.