CHICAGO — Monday night was breezy and calm in Grant Park, except for news vans humming, security guards trolling and a lone street musician strumming, “O-o-o-o-Obama!”

On the eve of Sen. Barack Obama’s Election Day bash here in the city where he forged his political identity, there was no sign of the estimated one million people who will gather here tomorrow night. The party, for now, was at Obama’s rally in Virginia.

But all that will change today.

Just five years ago, Obama was a state senator from Chicago’s South Side. Now his meteoric rise to political stardom culminates in today’s election.

And fittingly, the most important night of the Illinois senator’s political career will take place in the city where it started as the candidate, his campaign and a million supporters await the election in downtown Grant Park. He was scheduled to arrive in Chicago early today to cast his own vote in his Hyde Park precinct on the South Side.

Several taxi drivers said they have not noticed crowds yet. But they said they are dreading the full day of traffic expected today.

Most visitors — like Obama’s campaign entourage — had yet to arrive Monday. But in anticipation, transport officials advised visitors to park as far out as the airports and ride the train into town.

As the city prepped to be the center of attention today, the press corps lined up along Grant Park, where the event-planning firm the campaign has hired was setting up for tomorrow’s crowds. A new city of portable toilets, tents, American flags and police barriers has sprung up on the shores of Lake Michigan.

Scores of satellite uplink trucks jostled for position alongside the entrance to the site of the rally, and a few television news correspondents broadcast their initial dispatches from the entrance to where the rally will take place. Soaring overhead, the windows of a skyscraper were lit up to spell VOTE and the roof of the iconic John Hancock tower glowed red, white and blue.

Police are preparing for huge crowds around the park. While the official event is private, with 65,000 ticketed guests, news reports estimate that close to a million people will show up to Grant Park to participate in the rally, and by Monday night, streets passing through the park were barricaded and closed to vehicular traffic. Pods of police officers grouped themselves along the borders of the park.

Every police officer in Chicago will be on duty tomorrow, the Chicago Tribune reported.

Chicago’s mayor, Richard Daley, told the newspaper that there is no reason anyone should not be able to join the celebration.

“It’s a historic event,” he said. “If they want to be there, they should.”

Obama’s speech, preceded by live music acts, will be simulcast on jumbo-trons in the neighboring green space.

Monday’s daily presidential tracking poll from Rasmussen Reports had Obama ahead of his Republican challenger, Sen. John McCain of Arizona, by 6 percentage points.