CHICAGO -- Barack Obama beat out Hillary Clinton in Illinois for a home state victory Tuesday in a historic showdown between the two Democratic presidential hopefuls, while John McCain won the Republican race, according to FOX News projections.

Obama picked up the win in his home state after thousands of voters headed to the polls despite chilly and damp weather. The results came almost as soon as polls closed as  exit polling showed Obama winning nearly every demographic -- male and female, old and young, worried about the economy and angry over Iraq. Only among those older than 65 did Clinton manage to split the vote.

"Results will be coming in until late tonight, but we did just learn one piece of great news," Obama wrote to supporters in an e-mail. "Thanks to you, we're projected to win Illinois."

On the Republican side, McCain defeated Mitt Romney by splitting conservative votes with the former governor of Massachusetts, according to exit polls.

McCain, a former prisoner of war, won six in 10 moderates' votes and three in five votes from those who believe the Iraq war is the most important issue facing the country. Two in 10 in that category chose Romney and one in 10 chose former Arkansas Gov. Mike Huckabee.

More than six in 10 GOP voters approve of the war and four of 10 of those chose McCain while Romney won three in 10. McCain also defeated Romney in age groups, with most support coming from voters 65 and older.

Experts said the high-profile contest to decide who could become the first black or woman president, along with a host of other races, would likely lure a larger-than-usual flock of voters.  Election officials reported strong turnout -- perhaps record-setting.

Clinton too was raised in a suburb of Chicago, but chose to represent New York when vying for a Senate seat in 2000.

The Associated Press contributed to this report.