A one-time Democratic challenger to Sen. Arlen Specter (D) has endorsed Rep. Joe Sestak’s (D) 2010 bid to unseat the five-term Pennsylvania Senator.Lynn Yeakel, who narrowly lost to Specter in the 1992 general election, is scheduled to endorse Sestak on Thursday in Philadelphia. The endorsement will coincide with the launch of a Women for Sestak group.A little-known businesswoman at the time, Yeakel challenged Specter after seeing him question Anita Hill during Supreme Court Justice Clarence Thomas’ confirmation hearings. Yeakel narrowly lost to Specter, 49 percent to 46 percent. “I’ve known Joe for four years and he has the character and integrity to represent our party and our Commonwealth in Washington,— Yeakel said in a statement. “As one of Joe’s constituents, I can attest to his exceptional dedication to his work as a Representative, both in Washington and Pennsylvania.—Public polling has shown Specter with a significant lead over Sestak in the Democratic primary, which is scheduled for April. A Quinnipiac University survey from the end of September showed Specter led Sestak 44 percent to 25 percent. The same poll showed Specter and the likely GOP nominee, former Rep. Pat Toomey, in a statistical dead heat.