Despite costing us the Super Bowl, Boston is Mayor Tom Menino's city to lose. Given relative peace and prosperity, and the incredible challenge of defeating an incumbent, Menino will likely decide when and how his tenure as mayor comes to an end. Still, a rival politician can dream. The Globe today details three people who are weighing a run for mayor in 2009: --City Councilor at Large Michael Flaherty, 38, who's been having low-key......