Illinois voters overwhelmingly embraced Obama's message of optimism and unity to elect him and become only the fifth black U.S. senator in history.
With 27 percent of precincts reporting, unofficial returns show Obama with 81 percent (or 904,393 votes) and Republican Alan Keyes with 16 percent (or 178,393 votes). Two third-party candidates spit the rest of the vote.
The race was the nation's first Senate contest between two black candidates from the major parties. Obama will replace Republican Senator Peter Fitzgerald, who declined to run for a second term.