Chicago - Strangers chat about politics on the train and buttons peer out from coats with the smiling face of Chicago's favourite son, Barack Obama, as the city is gripped with excitement about the looming election.

But Chicago, population 2.7 million, is not just waiting for Tuesday night to learn whether the US senator from Illinois, who got his political start on the city's South Side, will become the first African-American president.

Not relying on polls that show Obama ahead of Republican opponent John McCain, Chicagoans instead gathered by the thousands at phone banks across the city, where they hoped to get out the vote in key swing states that will likely decide the next president.

At Obama's Illinois campaign headquarters in downtown Chicago, several rooms were filled with volunteers of all races, ranging in age from their teens to their 80s. They had filled several shifts each day, armed with mobile telephones and clip boards listing registered voters in neighbouring Indiana and Ohio. On the phone, volunteers reminded people to vote and told them where to find their local polling places.

The legions of volunteers backing up their candidates at events like the Chicago phone banks were part of a down-to-the-wire push by McCain and Obama in the final weekend before election day.

While the candidates traversed the country, holding rallies at the end of the record two-year campaign, volunteers went door-to-door handing out literature and conversing with potential voters in the drive to push turnout and convince those who remained undecided.

High school student Robert Stuart III, 17, falls just short of the voting age of 18, but he was convinced by a teacher to get involved in the campaign, and has been closely following Obama since 2004.

"Since I can't vote, I'll try to get others to do it," Stuart said.

Obama has inspired many of the students at Stuart's school to get involved, and Stuart worries that if his candidate loses an entire generation could become disillusioned with the political process. And though he knows no victory is assured, he believes his afternoons spent getting out the vote can make a difference.

"If I wasn't hopeful, I wouldn't be here," he said.

Nadine Kijak, 54, made more than 50 calls Sunday evening for Obama and is wary of the opinion polls that show her candidate with a decisive but not quite insurmountable lead.

"We can't assume because he's ahead we (don't need to) get out there," she said.

Kijak, an African-American who grew up in the segregated South and lived through the turmoil of the civil rights movement in the 1960s as a child, never thought she would see a black candidate come this far in her lifetime.

"It's inspiring to belive young black boys can see they can be president," she said, as she took an emotional look back a childhood in which she could not even visit a beach she longed to see because of the colour of her skin.

That sense of historical importance led some volunteers to bring along their young children - with one family of phone-bank callers spanning three generations.

In the constant stream of people coming in and out of the basement in the downtown office building that houses the effort, some had just dropped by looking for elusive Obama T-shirts, bumper stickers and yard signs.

For those using their mobile phone minutes to call complete strangers, a hand-lettered poster near the entrance stressed the urgency of their effort: "2 days left." (dpa)