Update: Hey, Tom Dart’s “in”.

Update II: The announcement:

View more news videos at: http://www.nbcchicago.com/video.

Update III: For a mayor who’s not known for his powers of articulation, it was a dignified, personal, and straightforward announcement. And, for a mayor of such tenure and power . . . very understated. Quiet, even. From a theatrical and rhetorical standpoint, it was very classy.

Update IV: Valerie Jarrett? Sounds plausible.

Update V: Anyone running should read Ramsin Canon’s Getting Past Daley.

Update VI: I like Miner’s take on the flipside of “Chicago’s going to suck to be mayor of”: “Only the worst demagogues can’t imagine anyone but themselves correcting their own mistakes.”

Update VII: As has been pointed out by several people on Twitter, if you can’t get enough talk about Daley, WBEZ’s on-air live chat is really interesting.

Update IIX Mick Dumke’s March 11 cover story, Time for a Revolution, is as good an explanation of any for Daley’s declining popularity. Accompanying the article, Dumke discussed 10 candidates to replace Daley; names not previously mentioned include Tom Allen and Sandi Jackson.

Eric Zorn isn’t surprised that Mayor Daley isn’t running for reelection, but my reaction is similar to Rich Miller’s: “My first thought is I never figured he’d go out while he’s held in such low regard.” And it’s not just declining popularity. Daley’s big projects of the past few years—in the wake of Millennium Park—have either been unsuccessful (the Olympic bid), troubled (O’Hare expansion, Block 37, the O’Hare express train), or unpopular (the privatization of the parking meters).

As for idle speculation, I’m just going with Occam’s Razor:

* His wife has been very sick, and the Mayors Daley, to their credit, have always struck me as devoted family men.

* It’s also a very, very tough climate to be an incumbent; it’s no coincidence that the upcoming elections will include not just a wide-open race for mayor but also for several City Council slots. The city is in a difficult financial situation, and it’s also going to get very little help in the near future from the American economy as a whole, which remains not just stuck in a recession but labors under a knotty disconnect between capacity and employment. Or from the federal government: the possible Republican takeover of the House—and even the Senate—leads me to think that no ambitious solutions are forthcoming as legislation becomes even harder to pass.

In other words, for a mayor with a penchant for big projects, Chicago just isn’t going to be very much fun to lead for the next few years. That, I think, is the simplest answer to Rich Miller’s quandary: being a good mayor in this specific period may not be the same as being a very popular one.

* Who will replace him? REPLY HAZY ASK AGAIN. Rahm Emanuel and Lisa Madigan are the only two remotely possible candidates who would be sure bets if either ran, but I wouldn’t bet on either actually running (maybe next time). My guess is that Bob Fioretti, Tom Dart, Scott Waguespack, Miguel Del Valle, James Meeks, Forrest Claypool, David Hoffman, and James Houlihan will all at least dip their toes in. Of those, maybe Tom Dart might be a frontrunner, but all this needs to sink in first.