The contest to succeed Ontario Premier Dalton McGuinty is about to have 3 contenders.  In addition to already declared candidates Glen Murray and Kathleen Wynne, Sandra Pupatello is expected to announce her candidacy for the Ontario Liberal Leadership here in Toronto this morning.  Pupatello represented the Windsor West riding from 1995 to 2011.  She held several cabinet positions after the Liberals came to power in 2003.  50 year old Pupatello left provincial politics last year and took a job at PricewaterhouseCoopers.  Mississauga South MPP Charles Sousa is also expected to enter the race for Liberal leader and Premier on Saturday.