Updated Wednesday, November 21, 2012 at 06:01 PM
WASHINGTON — U.S. Rep. Jesse Jackson, D-Ill., resigned from Congress on Wednesday, saying in a letter that he is cooperating with a federal investigation "into my activities" but blaming health problems for his decision to step down just two weeks after his re-election.
Jackson's letter to House Speaker John Boehner, R-Ohio, was his first public acknowledgment of the corruption investigation into his alleged misuse of campaign dollars.
"I am doing my best to address the situation responsibly, cooperate with the investigators, and accept responsibility for my mistakes, for they are my mistakes and mine alone," Jackson said in the two-page letter dated Nov. 21. "None of us is immune from our share of shortcomings or human frailties, and I pray that I will be remembered for what I did right."
Despite his admission of "my share of mistakes," Jackson said his deteriorating health was the reason he was quitting. He has been on medical leave since June while receiving treatment for bipolar disorder and other health problems.
"Against the recommendations of my doctors, I had hoped and tried to return to Washington and continue working on the issues that matter most to the people of the Second District. I know now that will not be possible," Jackson said in the letter.
The congressman could not be reached.
Jackson, 47, won re-election this month while being treated at the Mayo Clinic in Rochester, Minn., and issued a statement on election night saying he would return once his doctors approved.
He has not appeared in the House since June 8. It was later revealed that he was being treated at the Mayo Clinic for bipolar disorder and gastrointestinal problems. He returned to his Washington home in September but went back to the clinic the next month, with his father, the Rev. Jesse Jackson, saying his son had not yet "regained his balance."
In the run-up to re-election, the younger Jackson staged no campaign events and didn't even run a TV ad.
News of the resignation on the eve of Thanksgiving, when Congress was not meeting and many Washingtonians were traveling, seemed to take even members of Jackson's staff by surprise.
His press secretary, Frank Watkins, said Wednesday morning that he didn't know anything about a possible resignation. Watkins attributed the rumors to media speculation.
House Minority Leader Nancy Pelosi, D-Calif., said she had spoken to Jackson and his father.
"As he works to address his health, our thoughts and prayers are with him, his wife, Sandi, his children as well as his parents," she said.
The House adjourned Friday and reconvenes at 2 p.m. Tuesday. Protocol calls for Jackson's letter to be placed before the House on Tuesday and his resignation noted then, an official said. Normally the House has 435 members, but there is now one vacancy, so Jackson's will be a second.
Under Illinois law, Gov. Pat Quinn, a fellow Democrat, would call a special election to fill Jackson's seat in the 2nd Congressional District, which extends from Chicago's South Side to Kankakee.
Political insiders had been expecting Jackson's resignation.
He took office in 1995 after winning a special election. Voters in the district have said his family name and attention to local issues have been the reasons for their support. He began his career with a star power that set him apart from his hundreds of House colleagues.
But his resignation ends a once-promising political career tarnished by accusations that he was involved in discussions about raising campaign funds for then-Gov. Rod Blagojevich in exchange for an appointment to President Obama's vacated U.S. Senate seat. A Jackson emissary is alleged to have offered to raise up to $6 million in campaign funds for Blagojevich in exchange for the governor appointing Jackson to the seat.
The House ethics committee is investigating those accusations, which Jackson has denied.
Blagojevich is in federal prison after being convicted of trying to sell the seat, among other things.
Material from The Associated Press is included in this report.