Alexis Madrigal a senior editor at The Atlantic, has the scoop: the man behind @MayorEmanuel is Dan Sinker, who teaches journalism at Chicago's Columbia College.
UPDATE During the campaign, Rahm Emanuel offered a $5,000 charitable donation to whoever unmasked the identity of @MayorEmanuel. On Monday, Emanuel spokesman Ben LaBolt said in a statement, "Now that the cat is out of the bag, the Mayor-elect will keep his commitment to donate $5,000 to the charity of Prof. Sinker's choice. Details to follow in the coming days." END UPDATE
UPDATE2 LaBolt told me it will be a personal donation from Emanuel, not from his campaign fund. END UPDATE2
Writes Madrigal: "The genius behind @MayorEmanuel is Dan Sinker, who has a heart made out of Chicago and balls of punk rock."
Sinker almost was outed, writes Madrigal: "What's stunning is that Sinker managed to preside over @MayorEmanuel without ever getting caught. Or at least outed. His secret was known only by his wife, a small circle of friends, and one Chicago Public Schools teacher, Seth Lavin, who figured out Sinker's identity when Sinker used his personal bit.ly account to shorten a link that @MayorEmanuel later tweeted. Lavin kept it mum. Others came close to identifying him, Sinker said. An intern at the Wall Street Journal was onto him early, as was a reporter at Crain's Chicago Business. But no one could muster any proof."