Cook County Sheriff Tom Dart's decision to forgo a run for Chicago mayor is a political game-changer. Dart, who cited family duties as a factor in his decision at a press conference this morning, appears to have turned away from the mayoral race at the very brink of jumping in -- he had already hired two experienced political consultants to advise him.

Dart would have been a formidable candidate for mayor. His moratoriums on foreclosure-related evictions in 2008 and this fall have put pressure on unaccountable banks and raised the profile of people and neighborhoods caught in the aftermath of the housing bubble. His performance resolving the Burr Oak Cemetery scandal was praised, giving him an obvious way to engage Chicago's large black electorate. And Dart's political roots are in the influential 19th Ward, presumably allowing him access to the area's experienced election workers. 

As the presumed mayoral front-runner, Rahm Emanuel appears to be the biggest beneficiary of today's news; Eric Zorn thinks Dart's pass means the mayoral race won't even go into a run-off. The question now becomes who among the remaining candidates -- if any -- can fill the vacuum left by Dart's absence in this critical race? Can State Sen. James Meeks elevate his campaign? Can Gery Chico make the case that his experience as Mayor Richard Daley's right-hand guy means he's the best person for the job? Will Carol Moseley Braun, City Clerk Miguel Del Valle or Ald. Robert Fioretti (2nd Ward) step up with fresh ideas for a city facing big challenges? Let's hope so. As Greg Hinz put it in a blog post today:

Frankly, [the mayoral campaign] shouldn't be over. The last thing Chicago needs is an untested Mayor Emanuel to waltz into City Hall without detailing what he'll do and how he'll do it, without running the gauntlet that any big-city mayor needs to run to prove himself.