CHICAGO – Tracy Kelley told her boss that she stepped out to vote, but she didn’t know she’d be gone from work for two hours.

Like many, Kelley thought it would be convenient to vote before Election Day, but early voting sites throughout Illinois on Thursday resembled the day-after-Thanksgiving shopping rush as people stood in long lines to cast ballots.

More than 550,000 people have already voted across Illinois, state election officials say. That number was left far behind as people rushed to the polls on the last day to vote early.

In Chicago and suburban Cook County, 10,000 people voted within the first hour polls were open.

Despite the lines, Kelley, 39, waited along with hundreds of others in the maze-like hallways of the basement below city elections offices.

“I want Chicago’s numbers to be high,” she said. “It’s important to show we took this seriously even though we know the state is going to (Barack) Obama.”

There are about 7.7 million registered voters in Illinois. About 220,000 people cast ballots before Election Day in the February primaries, but this is the first time residents will have a chance to vote early in a presidential general election.

In many of the 30 other states that have the option, residents have taken years to become familiar with early voting and use it in large numbers, said Brian Gaines, a political science associate professor at the University of Illinois at Urbana-Champaign.

Intense voter mobilization efforts this year seem to have pushed Illinois past that stage, he said. The state implemented early voting just three years ago.

“All bets are off,” Gaines said. Illinois is “skipping the early learning curve,” he said.

And now that Illinoisans’ interest in early voting has been piqued, it will probably stay relatively high for years to come, Gaines said.

The popularity of early voting has already obliterated election officials’ expectations.

Associated Press Writers David Mercer in Champaign and Jim Suhr in Madison County contributed to this report