Steve Pagliuca, co-owner of the Boston Celtics, is weighing taking a shot at the late U.S. Sen. Edward M. Kennedy’s seat, according to a source close to the Weston resident. Pagliuca, who has also been considering buying the struggling Boston Globe, would join a heavily populated Democratic field that includes Attorney General Martha Coakley. Pagliuca declined comment when reached by a Herald reporter this afternoon, but a source close to the Bain Capital managing director confirmed the 54-year-old is thinking about joining the race. His candidacy is far from a slam dunk, but the well-financed candidate is expected to shake...