Ten investment groups offered to buy the Cubs, and more than 20 made proposals to purchase just Wrigley Field as a potential $1 billion sweepstakes began today for a pair of Chicago treasures. The favorite remains a group led by John Canning Jr., chairman of Madison Dearborn Partners LLC. Canning is a part-owner of the Milwaukee Brewers, the team once controlled by Baseball Commissioner Bud Selig. Canning and Selig remain close friends.