By Lisa Lambert and Sam Youngman
NASHUA, N.H./PENSACOLA, Florida (Reuters) - President Barack Obama and Republican challenger Mitt Romney campaigned feverishly in closely contested battleground states on Saturday but changed travel plans to avoid Hurricane Sandy, the massive storm approaching the U.S. East Coast.
With just 10 days before Election Day and polls showing the national race a dead heat, Romney was holding three rallies in Florida, whose 29 electoral votes are the biggest prize among states considered too close to call.
He told supporters that Obama was focusing his campaign on small things, and swore he would win the election, to chants of "Ten more days, 10 more days."
"Look into the future and see the debt that's being amassed and say, 'What is right for America?' This is a time of big choices, of big consequence. It's a big election," Romney said.
Obama spent Saturday in New Hampshire, whose handful of just four electoral votes could play a crucial difference in the tight race.
"Ten days, New Hampshire, 10 days and you'll be stepping into a voting booth and making a defining choice about the future of our country," the Democratic president told about 8,500 people, in a speech criticizing Romney's record on taxes and fees as governor of Massachusetts.
New Hampshire is known for its low taxes, and many of its residents moved away from Massachusetts to cut their tax bills.
Both campaigns were keeping a wary eye on Hurricane Sandy, which threatened to slam into the eastern third of the country on Monday or Tuesday with torrential rains, high winds, major flooding and power outages.
Romney canceled a trip to Virginia scheduled for Sunday, when the state is expected to begin feeling the impact of the approaching storm. The candidates are also running neck and neck there.
He will go instead to Ohio for appearances with Paul Ryan, his vice presidential running mate. Most polls give Obama a slim lead in Ohio, which has 18 electoral votes.
Obama rescheduled his departure for campaign dates in Florida to Sunday night from Monday because of the storm. His campaign has not yet said whether it would cancel or postpone an appearance with former President Bill Clinton on Monday in Virginia.
"We're closely monitoring the storm and will take all necessary precautions to make sure our volunteers and staff are safe," Obama campaign spokeswoman Jen Psaki said. "We can't predict, just as no one can predict, how the storm will impact local communities."
With widespread concern that power blackouts in Sandy's wake could interfere with early balloting, lines at early voting stations stretched for blocks at some polling stations in Maryland, which began early voting on Saturday.
Polling sites in Virginia were also busy.
Eager to avoid any complaints that campaigning distracts from handling a potential natural disaster, the White House pointed out that Obama was briefed about Hurricane Sandy on board Air Force One as he traveled to New Hampshire.
"This is an example yet again of the president having to put his responsibilities as commander in chief and as leader of the country first while at the same time he pursues his responsibilities as candidate for election," White House spokesman Josh Earnest told reporters.
In such a close election, Obama does not want to be seen mishandling Sandy. White House officials are keenly aware of the severe criticism that President George W. Bush received for failing to react quickly to Hurricane Katrina in 2005.
SPRINTING TO A DEAD HEAT?
The two election contenders are in a late sprint to ensure their supporters get out to the polls and to win over the dwindling pool of undecided voters in the eight or so battleground states where the election will be decided.
Obama and Romney remained in a statistical dead heat on Saturday in the daily Reuters/Ipsos online tracking poll. Obama led Romney by 47 percent to 45 percent, within the survey's credibility interval.
The poll also showed that support for the candidates was solidifying. Almost nine out of 10 of registered voters now say they will definitely vote for their candidate, leaving just 12 percent who say they could change their minds.
In contrast, an average of about 15 percent last week said they might still switch.
But more and more voters have already taken advantage of early voting programs and cast their ballots, despite the time remaining before Election Day. Eighteen percent of respondents in the Reuters/Ipsos poll said their votes were in.
The U.S. election is not a true national poll, but a state-by-state contest in which 538 electoral votes are divided among the 50 states and Washington, D.C., roughly according to population.
With the majority of states firmly Republican or Democratic, the fight for the "swing states" not firmly tied to either party is hugely important.
This year, there is a possibility one candidate could take enough states to win the electoral vote - and thus the White House - while trailing in the nationwide popular vote.
That last happened in the bitterly contested election of 2000, when Democrat Al Gore won half a million more votes nationally than Bush, but the Republican won the presidency because he ended up with more electoral votes.
(Additional reporting by Patricia Zengerle in McLean, Virginia, Writing by Patricia Zengerle; Editing by Alistair Bell and Peter Cooney)