Obama won election as Illinois state senator in 1996 under unusual circumstances. The incumbent, Alice Palmer, had initially decided not to seek reelection, choosing instead to run for a seat in the U.S. Congress. After losing to Jesse Jackson Jr., she applied to run for reelection for her State Senate seat. Obama’s campaign challenged whether Palmer and the other candidates had met the legal requirements, questioning whether they had acquired enough legitimate signatures. Election authorities determined that Palmer and other candidates did not have enough petition signatures, leaving Obama as the only candidate remaining. Palmer later endorsed Hillary Clinton for president in 2008.

Obama won reelection to the Illinois State Senate in 1998 and 2002. He remained in the Illinois State Senate until winning a seat to the U.S. Senate.