Jackson has been absent from Congress for months as he deals with both the federal investigation and mental health problems that have landed him at the Mayo Clinic at least twice. It has been rumored in recent weeks that he would resign as part of a plea deal.
His resignation means he will not be sworn in for the term he won in November. Despite not having actively campaigned for it, Jackson comes from a safe Democratic district and was easily reelected.
The resignation will trigger a special election, which will be declared by Gov. Pat Quinn (D) and must occur within 115 days of the vacancy.
Among the names being mentioned as replacements are Jackson's wife, Chicago Alderwoman Sandi Jackson (D), Cook County Chief Administrative Officer Robin Kelly (D), state Sen. Toi Hutchinson (D) and state Sen. Napoleon Harris (D), a former football player at Northwestern University and in the NFL.
Also being mentioned is former congressman Mel Reynolds (D-Ill.), who resigned the seat that Jackson won in a 1995 special election and was convicted on charges of child pornography and sexual misconduct with a 16-year-old campaign worker.
The seat should easily stay in Democratic hands. It went 82 percent for President Obama in 2008.