Election officials in storm-ravaged New York and New Jersey are moving dozens of polling sites and seeking backup power for hundreds more before the November 6 vote.
In New Jersey coastal areas hit hardest by Hurricane Sandy, authorities inspected the damage to see if communities needed new polling sites.
Some election supervisors gained access to barrier islands yesterday for the first time, after the New Jersey governor Chris Christie lifted an emergency declaration.
The north-east is recovering from the storm that killed at least 105 people in the US and initially cut off electricity to 8 million customers.
The country's energy department said yesterday that 3.5 million customers were still without power, including 2.7 million in New York and New Jersey.
Election planning in New York city "is still very much a work in progress" because "substantial areas in Queens and Staten Island have poll sites that are inaccessible", said Doug Kellner, co-chairman of the state election board.
About two dozen polling sites on Long Island's south shore and Staten Island pose "a very difficult situation", Mr Kellner said.
"There is going to be an election, and it won't be perfect, but we will do the best we can," he said.
New York, New Jersey and Connecticut were the areas most likely to experience election disruptions.
Polls project that Barack Obama, the US president, will easily carry the three states in his re-election bid against the Republican nominee Mitt Romney.
Election authorities have not had to cope with such extensive storm damage before, so it is difficult to project how the disruption will affect voter turnout, said Michael McDonald, a political scientist at George Mason University in Virginia.
"Just as a snowstorm or a bad thunderstorm on election day can depress turnout, it stands to reason there can be lower turnout as a consequence of Sandy," Mr McDonald said.
Storm victims "have much better things to do than vote at this point".
Mr Christie said trailers would be sent to areas without electricity so voters could cast paper ballots.
New Jersey's top election officer, Kim Guadagno, told all election and county clerks' offices to stay open at least eight hours a day until tomorrow for early voting. Voters can text their address to receive a response telling them where to vote, she said.
New York mayor Michael Bloomberg yesterday voiced frustration with the city's election board, saying it is "basically run by nobody".
The bipartisan board, independent of city government, must "find out what's happened to all the private buildings that have polling sites in them and then coordinate with us on public sites," the mayor said.
"Let's be nice and say they've had their problems," Mr Bloomberg said. "It's a shame that some bureaucrats would screw it up and hopefully that won't happen."