Rep. Jesse Jackson, Jr. (D-Il) resigned Wednesday, aides to House Speaker John Boehner (R-OH) confirmed to NBC News.
Jackson's letter of resignation, sent to Boehner, acknowledged that he was under federal investigation for alleged mishandling of campaign funds, and referred to his recent medical leave from Congress. Jackson wrote:
During this journey I have made my share of mistakes. I am aware of the ongoing federal investigation into my activities, and I am doing my best to address the situation responsibly, cooperate with investigators, and accept responsibility for my mistakes, for they are my mistakes alone. 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.
The 47-year-old son of civil rights leader Jesse Jackson had not made a public appearance since June, when he took a leave from the House. Jackson had recently been treated for bipolar disorder at the Mayo Clinic.
At the same time that he faced health problems, the U.S. attorney's office in Washington, D.C. was investigating claims that Jackson had used campaign funds for personal use. A source with the Justice Department told NBC News that no announcement was "imminent" in the investigation.
Jackson was also under investigation from the House Ethics Committee for his 2008 bid for President Obama's vacated Senate seat. A Jackson associate allegedly offered $6 million in campaign funds to then-Gov. Rod Blagojevich in exchange for an appointment to the seat, the Chicago Tribune reported.
Despite not campaigning for his seat, Jackson won re-election in his South Side Chicago district earlier in November.
Late Update: 3:30 p.m.
House Minority Leader Rep. Nancy Pelosi (D-CA) weighed in on Jackson's departure. Pelosi said that she had met with the former Congressman and his father, Rev. Jesse Jackson, earlier Wednesday afternoon.
"It is with great sadness that we learned of Congressman Jackson's decision to submit his resignation," Pelosi said. "His service in Congress was marked by his eloquent advocacy for his constituents' views and interests."
Pelosi added that she was grateful for his and his family's long record of public service to the United States.