CHICAGO – A state senator will face an investment banker-turned-teacher after each emerged as his party's nominee for a U.S. Senate race that could shape the balance of power in Congress. "This is going to be a contest of ideas," state Sen. Barack Obama said Tuesday after rolling up more than 50 percent of the vote in the Democrat primary, crushing six rivals. The 42-year-old former civil rights lawyer, who could become only the third black U.S. senator in a century, faces Republican Jack Ryan, a 44-year-old millionaire high school teacher who has been dogged by questions about his divorce...