In this very close US presidential election, early voting could be the deciding factor for which candidate wins the race - Barack Obama or Mitt Romney.
More than one-third of votes are expected to be cast before November 6.
All 50 states and Washington DC offer some type of early or absentee voting.
Early voting allows flexibility and convenience for people who may not be able to get to the polls on election day.
So far, according to the United States Election Project at George Mason University, 16 million Americans have already voted.
Obama's re-election campaign has concentrated on getting his party's supporters to the polls in advance because early voting was so influential in 2008.
Seventy-nine per cent of votes were cast early in Colorado, and they largely went for Obama. Obama won in the swing states of Colorado, Iowa, Florida, and North Carolina because of early voting.
Last week, Obama's campaign manager told reporters: "Every single day now is Election Day".
The president and first dady reinforced the message by voting early themselves.
Obama voted in person absentee while Michelle, his wife, mailed in her vote.
While the Obama campaign has made early voting part of its strategy, the Romney campaign isn't ceding the early vote.
They're also pushing their supporters to get to the polls now to prevent the early swell Obama enjoyed last time round.
A Gallup poll from October 29 found it may be working. Fifty-two per cent of those who have already voted cast their ballots for Romney. Forty-six per cent voted for Obama.
But Hurricane Sandy is complicating the get-out-the-vote early push, particularly in Virginia.
Local governments which administer early voting shut down in several key counties because of the storm.
Election officials promised polling places would be given a high priority for restoration of electricity following the storm.
As localities clean up after Sandy, it's unclear what the long term impact on the election will be.
The candidates have cancelled more than two dozen campaign stops because of the storm.
Obama will be off the campaign trail for at least three full days. And Romney has slowed his schedule and moved events out of Virginia to other swing states like Ohio.
But the storm could suck the wind out of his momentum by taking the national focus away from the race.
With only a handful of days left until the election, both candidates need as much time on the campaign trail as possible, taking advantage of every opportunity to shake hands and kiss babies to convince voters to commit early by casting a ballot before the big day.