I’ve covered a lot of Chicago mayoral races, going back to Harold Washington’s 1983 run—still the most exciting municipal election campaign I have ever witnessed.

I don’t claim to know everything about Windy City politics. But I do know this: Rahm Emanuel should think twice before giving up his day job.

Emanuel let slip earlier this year that, were Mayor-for-Life Richard Daley Jr. to ever call it quits, he might be interested in filling the vacancy.

Well, Daley’s quitting.

But don’t think that means that Barack Obama’s chief of staff is going to makean easy leap from DC to Chicago—a city he briefly represented in Congress during the interregnum that separated his tenures in the Clinton and Obama White Houses.

As the Chicago Sun-Times‘s very wise Lynn Sweet explains in a piece headlined "Rahm Has Money, But No Solid Base": "While White House chief of staff Rahm Emanuel is lionized in Washington, he would not start a mayoral race in Chicago automatically first in line to replace Mayor Daley."

Emanuel’s roots are only barely in Chicago, a city that takes neighborhood politics so seriously that it matters which side of the street you were born on.

Yes, he was born in the city. But he grew up in the suburbs, graduating from Winnetka’s New Trier West High School and the Evanston School of Ballet before heading off to Sarah Lawrence.

It is true that he once raised money for Mayor Daley and is close to some key local pols, including David Axelrod.

But when Emanuel ran for Rod Blagojevich‘s US House seat in 2002, he was opposed in the Democratic primary by former Illinois State Representative Nancy Kaszak, who drew significant union support and won 39 percent of the vote—despite being dramatically outspent by the former Clinton administration aide. Labor was angry with Emanuel for the role he played as a key proponent of the North American Free Trade Agreement, extending Permanent Most-Favored Nation Trading Status to China and other schemes that benefitted Wall Street and multinational corporations but accelerated the deindustrialization of cities such as Chicago and the loss of family-supporting jobs.

Nothing that Emanuel has done in the Obama White House will inspire confidence in him among the Chicago unions that feared his corporate-friendly politics in 2002.

Nor will his dismissal of advocates of genuine healthcare reform—including, presumably, Harold Washington’s personal physician, Dr. Quentin Young, national coordinator of Physicians for a National Health Care Program—as "f—ing retarded" endear him to Chicago’s Lakefront Liberals. (It didn’t exactly score him any points with advocates for the disabled either, despite the fact that Emanuel apologized to the folks who run the Special Olympics.) Progressive Change Campaign Committee co-founder Adam Green expressed a common sentiment with his observation that: "Rahm is unfit to represent Democrats in office. He’s a cancer on the Democratic Party. Democrats’ current 2010 situation is due to a weak Rahm Emanuel mentality that says water down real reform at the urging of Republicans and corporations, thus making Democratic reform less popular with voters than the real deal would have been. If Democrats had passed the overwhelmingly-popular public option and broken up the big banks when they had the chance, they’d be cruising for a landslide victory right now."

In truth, there are a good many progressives who would welcome a decision by Emanuel to exit the White House, especially if he would be so kind as to take Larry Summers and Tim Geithner with him. This is the "Chicago’s loss is America’s gain" way of thinking.

But of course that’s the real reason Emanuel is exceptionally unlikely to be the next mayor of Chicago. At this point in a difficult presidency, with mid-term elections less than two months away, the notion that the White House chief of staff would decamp to run for mayor of Chicago is over the top—even for Rahm. If Emanuel has a strength, it is his loyalty to his political employers.

If Emanuel were serious about running for mayor, he would need to move immediately, as the race to replace Daley is already in full swing—with credible candidates such as Sheriff Tom Dart on theverge of jumping in. Emanuel can’t stick around the White House through November and then decide whether he wants to run for mayor. Chicago takes its politics too seriously to wait for any man, even Rahm Emanuel.