BLUE BELL, Pennsylvania (AP):

Barack Obama, a former community organiser, is spending untold millions of dollars to identify and mobilise voters, and Republicans acknowledge that John McCain's team probably will be outspent and outmanned. They hope it won't be outmanoeuvred.

This is an unusual situation for Republicans, masters of the ground game: the contest of phone calls, door knocks, literature drops and text messaging that can make the difference in close contests. It's a contest so sophisticated on both sides that if you're a voter in their sights, chances are they've got a computer bar code just for you.

Narrow re-election

Look no further than the 2000 presidential race that showed Democrats and Republicans alike the importance of getting a party's supporters to polls. George W. Bush's disputed 537-vote victory in Florida gave the Republican the White House over Democrat Al Gore. Four years later, Democrat John Kerry ramped up the party's efforts but it wasn't enough to thwart Bush's narrow re-election.

This year, Democrats say they are determined not to let the White House slip from their grasp for a third-straight election and Obama has made turnout efforts a true priority. "We're waging a very aggressive campaign to use our network of neighbourhood volunteers to persuade voters wherever they are," said Jon Carson, Obama's national field director.

Difficult year

Republicans hope their battle-tested operation will deliver victory for McCain in a difficult year. They know the Democrats are pressing hard on the ground.

"They've definitely got the bodies, and they've definitely got the money," said Rich Beeson, the Republican National Committee's political director. Yet, what matters most is knowing whom to mobilise on Election Day, "and we've got the advantage there."

Both sides are mindful of this: Nothing else in the campaign matters if voters don't show up. Thus, Democrats and Republicans are combining new technological tools with time-worn shoe-leather tactics to find voters, persuade undecideds, rally hard-core backers and, the hardest part, get them all to the polling stations.