Jesse Jackson, a Representative in the House for a district in Illinois, resigned on Nov. 21 due to medical issues (Chicago Tribune).
Jackson was under investigation after he had perhaps inappropriately spent money earned during his tenure. Some of these expenditures include buying a $400,000 Rolex watch for a "female friend" and his furniture in his Washington D.C. home. The investigation was ran under the F.B.I's Washington Field House.
Jackson then left Congress due to medical purposes in June, in August said he being treated for bipolar disorder and then announced he is resigning in November.
The resignation could cost Illinois $5.15 million said the state board. This is due to elections having to be set up in the area. The Illinois primaries are on Feb. 26, but the earliest the district could have its primaries are in March (ABC News).