Billionaire hedge fund manager William Ackman, who joined other Harvard graduates in successfully calling for the university's president Claudine Gay to resign, is pressing forward with his efforts to reshape the Ivy League school's governance by backing a bid by four dissident alumni to join its board of overseers. The development represents a new challenge to the board, whose 30 members are typically nominated by the university's alumni association. Ackman's endorsement of the four write-in board candidates echoes his playbook as an activist shareholder, pursuing board seats at companies to push for changes.