Only one man in Chicago knew the identity of the Twitter superstar: @MayorEmanuel.

Who is he? How did he figure out the person behind the incredibly clever tweets? And why did he decide to keep it a secret?

Seth Lavin

Seth Lavin, 25, is a Chicago Public Schools 5th grade teacher, a husband, a new father — and the only man in Chicago who not only figured out who the fake Rahm Emanuel was, but also decided to keep his secret. We spoke to him on Tuesday.

How did you get involved in the fake Rahm Emanuel situation?

“Like a lot of people, I started out as a fan who was curious, and as I followed what @MayorEmanuel was doing, I started to sense patterns, clues, nuances, as to who the author might be,” said Seth Lavin.

“When Dan Sinker started tweeting was when Rahm Emanuel was still in Washington D.C., as President Obama’s chief of staff. During the November primaries, @MayorEmanuel was tweeting about things in Chicago, but also things about the state of the union,” he said.

Lavin figured out the author was a person who knew a lot about Chicago politics and journalism.

“At first I thought it was someone who was plugged in, maybe in Rahm’s inner circle. But then there were mistakes,” said Lavin.

For example, Lavin says Forrest Claypool came up in a tweet, and makes it sound as if Emanuel didn’t know him, but they did know each other well.

“Then there was a tweet mentioning Half Acre Beer, a local Chicago company. I knew it was a person watching from the Chicagoland area, so I had a smaller list in mind,” he said.

How did you figure out the identity of the fake Rahm Emanuel?

“You treat it like any problem that has an answer to it. A person puts hundreds of thousands of words on Twitter. He has to make a mistake. I made a list of people who were active Twitter users, who knew about Chicago politics, D.C. politics, and who had a sense of humor,” said Lavin.

When did you discover that @MayorEmanuel was Dan Sinker?

“I really figured it out later, during the blizzard in early February. My wife who was pregnant was a week and a half overdue. I took the day before the blizzard off of work, starting my paternity leave. So we were sitting at home snowed in, and I looked at the computer and said, ‘I’m figuring it out today,’” Lavin said.

Lavin says the clue to the author’s identity had to be at the beginning of the Twitter feed.

“I looked for an error in the beginning, before he became famous, before he was getting media attention. He had to have made a mistake,” said Lavin.

Sure enough, Lavin found what he was looking for. He discovered that Sinker set up an account at bit.ly, a url shortener. He used it three times and then stopped.

Lavin followed the trail. He went back and figured out that Dan Sinker created the bit.ly account and the link that he used had only been tweeted by @MayorEmanuel.

“He [Sinker] had come up in my list earlier. Everything about it checked out. He knew about Chicago, about journalism, politics. He even wrote an article about how Chicago mayoral candidates should be using Twitter to help their candidacy,” said Lavin.

Did you reach out to Dan Sinker once you found out?

“I emailed him and said, ‘You are @MayorEmanuel. I have no interest in outing you. In fact, I can tell you how to cover your tracks better,’” said Lavin.

Sinker responded, denying that it was him.

Lavin sent him another message stating his proof, i.e. the bit.ly account discovery.

“And I said, ‘it has to be you,” said Lavin.

So Sinker caved.

“He admitted to it and said, ‘are you going to spoil all this fun?”

So Lavin had to make decision.

“For him, for Chicago, for fun, for honor, it didn’t seem right to give him up. I didn’t say anything till now,” said Lavin.

Why did you decide to keep it a secret?

“There are two reasons. One is honor. I said to him, ‘I don’t have any plans to out you but I can tell you how to cover your tracks,’” said Lavin. “I talk to my students about integrity and want them to live in an honorable world.”

“The second reason: because it’s fun. He’s a modern Chicago folklorist. Someone who is capturing what the city is feeling when it doesn’t even know it’s feeling these things.”

“Getting attention for finding him out was way less interesting than finding out how he was going to end the Twitter feed. And it was worth it,” he said.

On being a teacher:

“I’m working as hard as I can to be as good a teacher as my students deserve. It is the most wonderful, rewarding and challenging job in the universe,” said Lavin.

“As good as it feels to have solved this mystery, it feels better to see that my kids are learning and moving towards college, which for them would be a huge step and would push them towards their dreams,” he said.

Have you spoken to Dan Sinker since he revealed his identity?

“He wrote me a very gracious e-mail afterwards, saying thanks for keeping it a secret,” said Lavin.

Fittingly, their Twitter interaction on Monday sums it up best:

Seth Lavin: @dansinker Finally, congratulations. (3:58 PM Feb 28th)

Dan Sinker: @SethLavin Thank you for keeping a secret. Best stranger I’ve ever trusted. (4:01 PM Feb 28th)

To see our interview with Dan Sinker, click the video below:

For a link to @MayorEmanuel’s page, click here.

To read all of @MayorEmanuel’s tweets in chronological order, click here.