Update 2:18 p.m.: Jackson Jr. has resigned by letter, and as Luke Russert reports, Speaker Boehner's aides have received the resignation: 

Aides to Speaker Boehner tell me they have received resignation letter of Rep. Jesse Jackson Jr.

— Luke Russert (@LukeRussert) November 21, 2012

NBC News's Mike O'Brien has a similar report.

An aide to Boehner confirms the speaker's received a resignation letter from Rep. Jesse Jackson Jr. (D-Ill.).

— Mike O'Brien (@mpoindc) November 21, 2012

Well, there's that. For now, Jackson Jr.'s website is still promoting inauguration ticket requests, which is a bit awkward since he just quit. But about that—Jackson won't be sworn in, but he won his seat pretty easily without even campaigning. And he comes from a Democratic district in Chicago. That said, who gets it?  The Washington Post's Aaron Blake reports,"The resignation will trigger a special election for his seat, which will be declared by Gov. Pat Quinn (D) and must occur within 115 days of the vacancy." The names being mentioned for that special seat include his wife, Sandi Jackson, State Senator Napoleon Harris, and Cook County Chief Administrative officer Robin Kelly. 

Original: After mysteriously disappearing from the Mayo Clinic a little over a week ago and keeping mum ever since, Rep. Jesse Jackson Jr. is expected to hand in his resignation to Speaker John Boehner this afternoon, the Chicago Sun-Times and the Chicago Tribune are reporting. "U.S. Rep. Jesse Jackson is expected to tender his resignation from Congress within the hour," a source close to Jackson told Mary Mitchell at the Sun-Times in a story that went up shortly after 12:30 this afternoon, and The Chicago Tribune has confirmed that report with Jackson's brother Jonathan Jackson. This news comes after Jackson Jr. reportedly canceled a conference call with his Chicago staff that was supposed to address his "future plans in politics" reports NBC Chicago. It's been a tumultuous two-week stretch for Jackson Jr.  Despite winning his seat easily on election night, reports that he was working on a plea deal with the feds for misusing campaign funds came the Friday after the results, and shortly after that he disappeared from the Mayo Clinic where he was receiving treatment for bipolar disorder. 

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Alexander Abad-Santos