After a frantic 20 months of rallies, debates and commercials in the most expensive presidential campaign ever, record numbers are expected to turn out for the most important US election in a generation.
Head to head: Obama and McCain face off in the most important US election in a generation
Across the country, state officials are preparing for record turnouts and huge lines at polling stations, a testament to the massive interest that has been generated in an election widely considered the most important in recent memory.
Some states are forecasting a turnout of 80 to 90 percent. That compares with nearly 60 percent in the 2004 presidential election, which itself was the highest participation rate since 1968.
"We will get closer to 100 percent turnout on election day this year than ever before," said Doug Chapin of electiononline.org, a non-partisan Web site run by the Pew Charitable Trust.
Tens of millions of people have already taken to the polls in recent weeks for early or absentee voting allowed in 31 states, including key battlegrounds Florida, North Carolina, Colorado and Nevada. As many as 40 percent of voters are expected to have voted before the election proper on Tuesday.
The election stands to make history regardless of which candidate wins Tuesday. John McCain, at 72, would be the oldest president to begin a first term, while Barack Obama, 47, would become the first African-American president.
Polls lean toward Obama
Obama has the ascendancy, but McCain has pledged not to give up
Opinion polls continue to give Obama a significant edge over McCain in the run-up to the general election.
The economic crisis, compounding George W. Bush's unpopularity, helped lift Obama and his message of "change" from a race that was too close to call in August to a significant lead in opinion polls during the closing weeks.
An aggregate of major national polls compiled by realclearpolitics.com gave Obama 50.7 percent to McCain's 44.3 percent as of Sunday night. Of those heading to polling stations early, registered Democrats have outnumbered registered Republicans in some states by 2 to 1.
The closing pre-election poll of Gallup-USA Today published Monday gave Obama a lead of 11 points -- 55 percent to 44 for McCain.
A new Wall Street Journal-NBC News poll put Obama ahead on 51 percent to 43, while CNN's latest poll on Sunday had Obama with a 53-46 percent edge.
McCain remains upbeat
McCain has warned against writing off his chances in the coming election
But McCain's campaign has vowed a comeback in the final days, pointing to polls that show as many as one in seven voters remain undecided.
"My opponent is measuring the drapes at the White House," McCain said, as he wrapped up a frenzied day of campaigning with a midnight rally in Miami. "The Mac is back. And we're going to win this election."
In an election climate stacked against the incumbent Republican Party, both Obama and McCain have promised change from what they call the failed policies of the last eight years.
"This is a defining moment in our history," Obama wrote in an article published in The Wall Street Journal. "Tomorrow, I ask you to write our nation's next great chapter... If you give me your vote, we won't just win this election -- together, we will change this country and change the world."
The next president will inherit the quagmire of the war in Iraq
The next president will assume the mantle in January in the midst of two wars, an economy tail-spinning into recession and a global financial system on the verge of collapse.
McCain has leaned hard on his self-styled "maverick" image, unafraid to take on his own party in the US Senate, while touting his 26 years in Congress, military career and expertise in foreign policy as making him the safer choice.
Obama has consistently sought to link McCain with the Bush administration, and his campaign was given last-minute fodder when Vice President Dick Cheney said he was "delighted" to support McCain in a weekend speech in Wyoming. Both Bush and Cheney have been otherwise absent from the campaign trail.
The looming recession has become the dominant force in the race since September, overshadowing major foreign policy issues like the wars in Iraq and Afghanistan, Iranian and North Korean nuclear activities, and a resurgent Russia.
Volunteers from both sides made millions of phone calls and knocked on millions of doors over the final weekend, while the campaigns made last-minute pleas for donations to mount massive television advertising.
Obama's campaign has been fuelled by an unprecedented fundraising prowess that comes mainly from small donors over the internet. Obama raised more than $600 million over the last 20 months, nearly twice as much as McCain, according to the Federal Election Commission.
Yet McCain's campaign manager, Rick Davis, predicted that his side would outspend Democrats by 10 million dollars in the final week.