CHICAGO — Buoyed by voters embracing his message of change, Barack Obama routed Hillary Clinton in the Illinois primary on Tuesday, a home-state victory that also offered them one of the richest prizes in the nation. Sen. John McCain defeated former Massachusetts Gov. Mitt Romney on the Republican side.

The Associated Press made the calls based on surveys of voters leaving the polls.

Obama and Clinton are locked in a nationwide battle for Democratic delegates in their historic bid for the White House. Illinois offered them each a share of 153 delegates. It trails only California and New York in Super Tuesday states.

The high-profile contest to pick the first black or female presidential nominee helped lure tens of thousands of early voters in Illinois, where bad weather arrived during evening rush hour as some of the state's 7.1 million registered voters scrambled to get to the polls.

At Beulah Shoesmith Elementary School on Chicago's South Side, Obama and his wife, Michelle, were greeted by cheers as they arrived to cast ballots. Obama shook hands with the crowd and shouted, "Are you fired up? Are you ready to go?"

Casey Beck, a 19-year-old sophomore at Eastern Illinois University in Charleston, said he cast his first-ever vote for Obama — and against Clinton. His top concern was the war in Iraq, where some of his high school classmates are serving.

"I want us to get out of Iraq (but) I don't want us to just leave Iraq and it turn back the way it was," he said. "I don't think Barack would do that."

John Topliffe, a 60-year-old retired Air Force pilot from the St. Louis area, voted twice for President Bush. But he backed Obama in the primary.

"Fairly early, I noticed that he kind of stood above the rest, above the fray and all the baloney," Topliffe said. "I put him with John Kennedy. I think he's got the same intelligence, the same charisma. I think he'd be a good president."

Illinois traditionally holds its primary in mid-March, when results in early states have often settled the nominees. This year, state lawmakers moved the primary up to give a boost to Obama, the freshman Illinois senator who began his campaign almost exactly a year ago. Clinton, the New York senator who grew up in suburban Park Ridge, focused her efforts on other states.