Chicago, Illinois - As Chicago braced for a throng of 1 million people at a public park in anticipation of Democrat Barack Obama's victory Tuesday, Republicans Monday were wishing them bad weather and a cliff-hanger election.

"I hope the million or so people who are planning to gather in Chicago have a long, cold night," quipped Mitt Romney, the former Massachusetts governor who lost his Republican bid for the presidential nomination to Senator John McCain.

Although election results are expected to start coming in about 0100 GMT Wednesday, western states could play a big role this year, with results expected to filter in well after 0300 GMT.

With massive voter turnout expected and new equipment in many states, the night could get much longer before a winner can be declared.

Broadcaster NBC said McCain and Obama were storming through a total of 22 states on Monday to shore up narrow margins and get out the vote in swing states.

Obama, who would be the first black president in US history, is the strong favourite in Tuesday's vote. An aggregate of major national polls compiled by realclearpolitics. com gave Obama 50.7 per cent to McCain's 44.3 per cent as of Sunday night.

But nationwide numbers are less important than capturing states with big electoral votes in the US indirect election method. Battleground states include Florida, Ohio, and Virginia - which hasn't voted Democratic since 1964 but is leaning toward Obama.

The Chicago celebration is to take place in Grant Park, along windy Lake Michigan, normally an ice box at this time of year. But weather forecasters expected record highs of up to 22 to 24 degrees Celsius - a good omen for the outcome for superstitious Obama fans.

Grant Park was the scene of massive demonstrations during the 1968 Democratic convention, when opponents of the war in Vietnam protested the nomination of vice president Hubert Humphrey after president Lyndon Johnson stepped out of the race. Many were injured in massive clashes with the police.

Chicago Mayor Richard Daley was expecting a different kind of event on Tuesday, saying: "It's a historic event. If (people) want to be there, they should."

The Obama campaign's permit anticipates 65,000 ticketed guests and 7,500 "participants" at the official fenced area, the Chicago Tribune reported.

But Daley says numbers outside the fence could reach 1 million as Chicagoans gather in anticipation that the man who has adopted their city as his own will win. (dpa)