SPRINGFIELD, Ill. — The weather turned frigid in the state capital on Wednesday, just in time for the dedication of a marker commemorating the day nearly 16 years ago when thousands braved single-digit temperatures to see then-U.S. Sen. Barack Obama announce his 2008 presidential bid from the steps of the Old State Capitol. The roughly 47-inch-by-44-inch marker, which stands on the southeast corner of the Old Capitol grounds in downtown Springfield,also commemorates Obama’s 2008 announcement that then-Sen. Joe Biden of Delaware would be his running mate. It adds historical resonance to a build...