CHICAGO — The last decade was lousy for Illinois Republicans. They lost a Senate seat, their party’s last governor went to prison and they were shut out of every statewide office. But the recent surprise win by Scott Brown in the Massachusetts Senate race and a string of setbacks for Illinois Democrats have Republicans giddy about their chances to claim the next big election prizes: President Barack Obama’s former Senate seat and ousted Gov. Rod Blagojevich’s old job.