Katy Wolpoff / NBC Chicago Jesse Jackson Jr. won re-election to Illinois' 2nd Congressional district by a landslide Tuesday night, NBC Chicago reported.

CHICAGO — U.S. Representative Jesse Jackson Jr., who has made no public appearances since for several months amid illness and who faces a criminal probe into alleged misuse of public funds, easily won re-election to his Chicago-area district on Tuesday.

Jackson, a Democrat who has served in the U.S. House of Representatives since 1995 and who was diagnosed earlier this year with bipolar disorder, won re-election to Illinois' 2nd Congressional district by a landslide, beating his two opponents, Marcus Lewis and Brian Woodworth.

As of 2 a.m. local time Wednesday (3 a.m. ET) and with 99 percent of precincts reporting, Jackson had captured 63 percent of the vote.

"My deep and sincere thanks to the people of the 2nd Congressional District, I am humbled and moved by the support shown today," Jackson said in a written statement. "Everyday, I think about your needs and concerns. Once the doctors approve my return to work, I will continue to be the progressive fighter you have known for years. My family and I are grateful for your many heartfelt prayers and kind thoughts. I continue to feel better everyday and look forward to serving you."

Jesse Jackson Jr. under federal investigation over alleged financial improprieties

Jackson reportedly spent the night at the Mayo Clinic in Minnesota.

August 2012: Former Rhode Island U.S. Rep. Patrick Kennedy visited longtime friend and colleague U.S. Rep. Jesse Jackson, Jr., who is undergoing treatment for bipolar disorder. Kennedy described their mutual struggle with depression in this extended interview with NBC News.

Jackson disappeared from public view before the primary when he left for a treatment center in Arizona in early June. He later moved on to Mayo where he was diagnosed with bipolar depression and gastrointestinal issues.

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In October, federal prosecutors and FBI agents in Washington, D.C., launched a criminal investigation into Jackson involving alleged financial improprieties.

At the same time, a House Ethics Committee continues to look into Jackson's supposed involvement in trying to be appointed to now-President Barack Obama's seat in the U.S. Senate. Jackson has admitted he wanted to be appointed to the Senate, but has repeatedly denied allegations he sent emissaries to offer campaign cash to then-Gov. Rod Blagojevich in exchange for the seat.

The emissary that he denies sending to negotiate with Blagojevich, Raghuveer Nayak, was arrested on 17 counts of fraud in June.

Once a rising star, the Illinois Representative has not been seen in Congress since early June. Friends and colleagues say Jackson was being treated at a facility in Arizona. NBC's Andrea Mitchell reports.

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