Chicago ? State Sen. Barack Obama, a former civil-rights lawyer seeking to become just the third black U.S. senator in a century, easily won the Democratic primary Tuesday, setting up a high-stakes fall race with Republican Jack Ryan that could decide who controls the Senate.

Obama, 42, rolled up big margins in both Chicago and its Cook County suburbs, trouncing his nearest rival, state Comptroller Dan Hynes.

Obama, a Harvard-trained lawyer whose father was a government official in Kenya, had 53 percent of the votes, to 24 percent for Hynes, with 95 percent of precincts reporting.

Ryan, a millionaire investment banker-turned-teacher, defeated seven other candidates to capture the GOP nomination. Ryan had 36 percent of the votes to 23 percent for his closest rival, dairy owner Jim Oberweis.

Obama and Ryan will compete in November to fill the seat of retiring GOP Sen. Peter Fitzgerald. National party leaders view the Illinois election as a crucial race in determining who will control the Senate, where Republicans have a 51-48 edge, with one Democratic-leaning independent.