CHICAGO (CBS) — Mayor Rahm Emanuel said, as a candidate for governor, his friend Bruce Rauner should make his full income tax returns and supporting documents public.

“Running for office and releasing your tax returns is like a rite of passage. You have to do it,” the mayor said Tuesday.

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WBBM Newsradio Political Editor Craig Dellimore reports Rauner, the Republican challenger in the race for governor, so far has released only three years of basic tax forms, without detailed supporting documents such as his tax schedules. He has requested a six-month extension on his 2013 tax returns, and his campaign has said the 2013 return will be made public before the Nov. 4 election.

Emanuel is supporting Democratic Gov. Pat Quinn’s bid for reelection, but is good friends with Rauner. He said he’s always made his own full tax returns public, including the supporting schedules, and Rauner should do the same.

“They speak to what I think is the right thing to do, and it’s a rite of passage running today for office, especially chief executive,” Emanuel said.

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He said he disagrees with Rauner’s decision not to release the schedules that were filed with his returns.

“I released my taxes when I ran for mayor. I released my taxes when I wasn’t even running for mayor. I released taxes when I was [White House] chief of staff, even though it was not an elected office, but it was an office in the public trust,” he said.

At an event in Springfield, Rauner laughed when reporters told him what Emanuel said, and quipped that everyone is entitled to his opinion.

“We have released far more than is required under the law. We have released multiple years of our tax returns,” he said. “People say release 2013. We will. 2013 hasn’t been filed.”

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Rauner has said releasing his basic tax returns is enough, and he’ll do that with his 2013 taxes in October.