Wulff announced his resignation Friday, a day after a request by prosecutors for Parliament to lift his immunity from prosecution over his relationship with a film producer in his previous job as governor of Lower Saxony. Those benefits allegedly included paying for a luxury hotel stay in 2007.
Wulff said in his resignation he was convinced he would be fully cleared of any wrongdoing.
Chancellor Angela Merkel, who proposed Wulff for the presidency in 2010, is now seeking an agreement with main opposition parties on a new head of state.
A successor must be elected by a special parliamentary assembly within 30 days.
The Associated Press contributed to this report.