Richard Shiro, Associated Press
Republican presidential candidate Herman Cain, speaks at the CBS News/National Journal foreign policy debate at the Benjamin Johnson Arena, Saturday, Nov. 12, 2011 in Spartanburg, S.C. The debate covered foreign policy, which has gotten little attention from the GOP candidates in recent weeks. During the debate Cain said President Barack Obama has been on the wrong side of nearly every situation in the Arab world and the United States has mishandled the uprisings in the region.

WASHINGTON — The lawyer for a Chicago woman who has accused Republican presidential candidate Herman Cain of inappropriate sexual conduct says a witness will go public Monday to support her claims.

Attorney Gloria Allred said a previously unidentified ex-boyfriend of Sharon Bialek will share what Bialek told him about Cain making an unwanted sexual advance in the late 1990s when he headed a Washington trade association.

The new information could provide the first corroborating details of the incident.

Cain has denied behaving inappropriately with anyone. He also denied knowing Bialek.

Bialek is the first of Cain's accusers to go public. Bialek said she had met Cain in Washington to seek advice after losing her job at the association. At least three other women have claimed that Cain sexually harassed them.