WASHINGTON - US President Barack Obama and Republican challenger Mitt Romney are neck and neck in opinion polls, but there is one area in which the incumbent appears to have a big advantage: those who have already cast their ballots.
Obama leads Romney by 59 percent to 31 percent among early voters, according to Reuters/Ipsos polling data compiled in recent weeks.
The sample size of early voters is relatively small, but the Democrat's margin is still well above the poll's credibility interval - a measurement of polls' accuracy - of 10 percentage points.
With the November 6 election just more than three weeks away, 7 percent of those surveyed said they had already voted either in person or by mail.
The online poll is another sign that early voting is likely to play a bigger role this year than in 2008, when roughly one in three voters cast a ballot before Election Day. Voting is already under way in some form in at least 40 states.
Both the Obama and Romney teams are urging supporters to vote as soon as possible so the campaigns can focus their door-knocking and phone-calling operations on those who are still undecided or need more prodding to get to the polls.