US ELECTIONS 2008: From James Cusick in Washington DC

Americans like waving their national flag. The Stars and Stripes is bigger than the Statue of Liberty or the Lincoln Memorial; unifying, instantly recognisable and there to celebrate whatever you choose, whether it's a returning astronaut or an aspiring president. Barack Obama's election campaign has spent $140,000 on American flags. John McCain's campaign has spent $7000. With only today and tomorrow left before Tuesday's final day of voting in the 2008 presidential race, we'll soon know if Obama got it right, or whether McCain may yet need to buy more flags.

With the leading US national opinion polls giving Obama a lead over McCain of between five and eight points, it's the Democrats who are coming into the last weekend with the greatest optimism. But at Obama's national headquarters in Chicago, Illinois, a marginal narrowing of the gap between the two presidential contenders has been enough to refocus their remaining energy on the state contests that will decide who wins the White House on Tuesday.

Those with political experience of past contests know the last weekend can be crucial. Steve Schier, an analyst at Carleton College in Minnesota, says the last weekend can be a "weird time in a presidential race. It's when the last of the voters who haven't been paying attention tune in, and the last of the undecideds make up their minds. Strange things can happen."

There's an accepted wisdom that the near collapse of the global banking system in September and October and the slew of rescue operations that were mounted from Wall Street to Threadneedle Street, has limited the potential of any last-minute surprise. The bail-outs and still-unresolved economic crisis left McCain looking like a shredded flag-waver for the discredited economic policies of the Bush years.

But that's not how they want things to look or feel over these last 48 hours on the 11th floor offices at 233 N Michigan, Obama's national campaign headquarters. The 33,000 square feet that used to belong to the Accenture consultancy is now engaged in a different business - putting Barack Obama in the Oval Office. And to do that, opinion poll leads have to be ignored and their game intensified in the swing-state battlegrounds that still matter, just as they mattered to Al Gore in 2000 and John Kerry in 2004.

For the two candidates, state capitals and key districts in Ohio, Florida, Missouri and Colorado, and a few others, will be treated like mere stops on an underground map as the Obama and McCain teams fight for the 6% of voters that are said to undecided and therefore still capable of upsetting the predictions of even the most conservative of opinion polls.

Any late event, any late mistake, and the wider outcome of the lengthy presidential race could be at stake.

Four years ago the late surprise came in the form of Osama bin Laden and the release of a video tape that held the power to remind voters that national security was still an issue. For John Kerry the tape was the last thing his campaign needed. For George W Bush it was the event that took him over the line in the key swing states.

Obama's campaign manager, David Plouffe, who has overseen the spending of a record war-chest of $640 million - more than the combined total budgets of the Bush and Kerry campaigns of 2004 - will want the final bang for all these bucks to be felt where it matters.

Having watched last week, almost helplessly, as the Obama campaign spend $1m a time on each of three major television networks, CBS, NBC and Fox, plus more money on black and Hispanic channels, to air a special half-hour political "infomercial", McCain's Arizona-based national headquarters know the pain of being the under-spending underdogs. Obama has raised $400m more than McCain, has 700 field offices across the US compared to McCain's 400, and with Obama's specialist polling costing $3.8m, compared to McCain's $1.1m, it will this weekend come down to where both team believe their remaining resources can be best targeted.

Inside the glass walls of Plouffe's 11th-floor office there may be a temptation for discussions to drift off and to imagine what the accommodation will be like in the West Wing. But for Obama's chief strategist, David Alexrod, it will be the final swing across Florida and Ohio, the states that can make or break, that matters now. The West Wing, for Alexrod, will be worried about after Tuesday.

Florida and Ohio have high-count winner-takes-all electoral college votes which go towards determining who actually wins on Tuesday, regardless of the overall popular vote. National polls reflect how the wider US feels about each candidate, but it's the arithmetic of the big states and the "toss-up" states that matter to people like Alexrod.

The winning post is 286 "electoral votes" - the system that has the winning candidate of each state assigned votes, mostly based on population. California has 55 college votes and is solid Obama. So is New York with 31, and Illinois with 21. Texas with 34 electoral votes is solid McCain, so is Arizona with 10 votes.

Obama's overall lead in the poll is reflected in his lead in "solid" states - some 196 electoral votes to McCain 140 "solid". In states merely "leaning" towards Obama there are 90 votes at stake. Those "leaning" towards McCain accounts for only 23 electoral college votes.

But just as it was in 2000 and 2004 it's the "toss-up" or the swing states where the final result may yet be determined. Around 89 college votes are still to be decided in tossup states such as Nevada, Missouri, Indiana, Ohio, North Carolina and Florida, with the combined total of just Florida and Ohio adding up to 47. It is therefore no great surprise that in the last weekend its visits to the Sunshine state and the Buckeye state that have been marked as crucial by both campaign teams.

John F Kennedy was the last US president not to win Ohio and yet still get to the White House. Every president since has viewed Ohio as the bellwether state.

In Alexrod's office, and indeed in all the state headquarters of both candidates' teams, the electoral map of the US is the treasure trail that needs to followed till the gold is finally located on Wednesday. For McCain, the recent marginal narrowing in the national polls is reflected in an optimism that Florida remains a winnable target. But that optimism has to be tempered by the four-point lead Obama now has in Ohio, up two points from last week.

But with the Rasmussen polling organisation estimating that 4% of the Buckeye state remains undecided, and some 10% of the current pro-Obama voters saying they could yet change their mind, it is still an open contest.

With the margin of victory on Tuesday likely to be small, and far from the landslide being predicted in the post-storm climate of the financial crisis, it's is no surprise that lawyers are already in place and circling for any repeat of 2000.

In Jacksonville, Florida, there is a substantial worry in the black community that a repeat of eight years ago may happen again. Then, 27,000 votes in Duval County were disqualified, with most of the thrown-out votes cast in predominantly black and Democrat territory.

That Gore lost Florida to Bush by just 537 votes highlights just how important water-tight voter registration will be this time round. Already some 10,400 people who registered to vote in Florida have found that discrepancies between their personal state records and their voter registration forms, means their democratic contribution in 2008 is already null and void. And No match, no vote' affects black voters far more than the white community.

The ghost of Floridas past, with concerns over everything from adequate application of registration rules to the casting of "provisional" ballots, which are allowed on polling day but only routinely counted days after the result is known, has meant the Democrats planning for 5,000 lawyers to be out in force on Tuesday monitoring the electoral laws.

In Ohio there are similar concerns. In 2004 Bush's winning margin over Kerry was 118,000 votes out of a total of 5.7 million. But estimates for 2008 say the state has 665,000 new voters who have registered, meaning that in this crucial swing state there is a real possibility of election officials being overwhelmed by a record turnout, with an army of lawyers challenging any attempt to have provisional ballots used that will not count towards the "first" total. Even the rules of any recount could yet be a legal battleground.

State officials in Ohio insist they have things under control. They say they have more voting machines than in previous years, they say that as much as a third of the state have used the option to cast their votes early and have promised everything will run smoothly.

If come Wednesday morning someone has not won comfortably and one of the candidates has yet to acknowledge the winner, America's democracy will once again be heading into the courtroom. A potential landslide for Obama may yet turn into a very long Tuesday night and Wednesday morning.