UPDATED 10/27/10 9:21 p.m.

CHICAGO (CBS) – Cook County Sheriff Tom Dart will not be running for mayor of Chicago.

“To both run for mayor and to be mayor is not something that I’ll be doing,” Dart said at a news conference outside the Cook County Criminal Courthouse and Jail Complex Wednesday morning.

Dart had been considered one of the frontrunners to succeed Mayor Richard M. Daley. But he decided he would not run, because of the attention it would take away from his family.

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“I’ve been thoroughly exploring a run for the mayor, and it’s been an exciting idea to be mayor,” Dart said. “The unfortunate thing for myself, though, is that I have found it impossible for myself to make being a mayor and a candidate compatible with being a father and a husband.”

Dart is married and has five children — the youngest 1 year old, the oldest 9.

“The timing just isn’t right right now for my family, and there’s just no other way to put it,” Dart said.

Dart told CBS 2 Chief Correspondent Jay Levine that his family and personal life was the only factor that played a role in his decision not to run, not fundraising or any other factor.

“I wish I could tell you there was some other dynamic, but there really isn’t,” he said, “This is a personal one.”

Dart said he was also focused on his post as Cook County Sheriff, particularly on foreclosures. He is up for re-election for that office this coming Tuesday.

Dart said he would “never forgive” himself if he were forced to put politics ahead of his family.

“I really can no longer look at my family and say ‘You know, this is the cost of doing business kids; that you happen to have a father in public life and you’re just not going to see me and good luck with everything,’” Dart said.

Dart said his current job is “very consuming” as it is, but not nearly as consuming as campaigning for mayor and running the city would be.

“I work 10-11 hour-days here, but there’s still time for me to be with my family in an appropriate way,” he said, but, “with the issues facing the city, that wouldn’t be possible.”

That isn’t to say that Dart thinks that it’s impossible to be a good father and a good mayor at the same time.

“I suppose if times were flush and the city was looking down the road at a very, very easy budget cycle coming up, you would probably sit there and say … well, not that you could ever take a job for granted, but it would not be as demanding,” Dart said.

Predicting Dart’s decision not to run would have been like reading tea leaves.

Just several weeks ago, Dart said, “I can’t see anything that could stop me” from running for mayor.

But when there was no announcement for several weeks after Mayor Daley announced he wouldn’t seek a seventh term – and there were indications Dart was going back and forth about a bid for mayor – one might have suspected he’d seen something new.

Then there was the body language of Dart and aides as they approached reporters outside Cook County Jail Wednesday morning. They didn’t exactly display the dress or demeanor of a campaign team ready for the fight of its life or one that had spent the last two months gearing up for one.

When asked if his decision not to run meant “clear sailing” for another candidate such as Rahm Emanuel, Dart said the voters would make up their own minds.

“The voters are very shrewd, and they’re not going to have anybody tell them, ‘This is who to vote for,’” he said.

Dart also said he does not plan to endorse any candidate.

Chicago being Chicago, there are some who question whether family concerns are really the reason for Dart’s decision. But whatever the reason, Dart is out and that’s certain to set off a mad scramble of candidates for his considerable base of supporters.

“I think the scramble is definitely on. And it’s certainly on, especially amongst the old guard white ethnics who still are in the City Council,” said Mike Noonan, chief strategist for likely candidate Carol Moseley Braun.

“I think everybody’s going to be interested in speaking to the voters who might have been inclined to support Tom Dart,” said Carol Moseley Braun.

“Tom and I are both from the South Side, I think that that meant that we were probably vying for some of the same support in some of the same places,” said Gery Chico.

Dart’s departure leaves Emanuel the remaining 800-pound gorilla in the race, and many wondering why Dart did an abrupt 180 after all but promising to run.

“With the money and the power that Rahm’s commanding and the still-crowded field, maybe he just felt like he needed to sit back and wait,” said Esther Cepeda of Chicago Sun-Times.

When asked if he scared Dart away, Emanuel replied, “I don’t think you can scare Tom Dart away.”

Emanuel – with three children between 10 and 13 – said he understood what Dart was going through.

“I take Tom Dart at his absolute word and you should honor that and respect that, knowing full well he had a serious gut check on that,” Emanuel said.

“Maybe Tom just didn’t have the fire in the belly for this fight at this time,” said Dan Proft. “To me, that seems plausible.”

Whether it was fire in the belly or family pressure, the result is the same: a clearer path for Emanuel, and perhaps new life for Gery Chico and other candidates, who might not have stood a chance in a Dart-Emanuel race.

CBS 2 Political Producer Ed Marshall contributed to this report.