With one week left the storm will dominate the news and distract a nation of voters

Superstorm Sandy tore into the U.S. presidential race as President Barack Obama and Republican rival Mitt Romney cancelled campaign events, punching holes in their carefully mapped-out strategies for the final week of one of the closest contests in recent history.

Seven days before the election, both men and their running mates tempered their campaigns for Tuesday, eager not to appear out of sync with more immediate worries over flooding, power outages, economic calamity and personal safety. Neither Mr. Obama nor Vice President Joe Biden planned to campaign. Mr. Romney was going forward with a planned event in Ohio, but his campaign said its focus would be storm relief.

The storm will dominate the news and distract a nation of voters during the crucial handful of days that remain before November 6.

“When the nation’s largest city and even its capital are endangered, when so many people are in peril and face deprivation, it’s hard to get back to arguing over taxes,” said historian and presidential biographer Douglas Brinkley.

Millions were left without power as the deadly storm whipped its way through presidential battlegrounds like North Carolina, Virginia and New Hampshire and sprawled as far as the Great Lakes, where gales threatened Ohio’s and Wisconsin’s lakeside regions.

Mr. Obama shifted from campaign mode to governing, abandoning a Florida event on Monday with former President Bill Clinton to return to Washington. He received a briefing from his top emergency advisers, his second in as many days. He addressed reporters at the White House, warning that recovery from the giant storm would not be swift.

Mr. Obama also expressed concern over the storm’s effect on the economy, and the disruptions in New York’s financial district were bound to be among those that preoccupied the administration on Tuesday. Storm damage was projected at $10 billion to $20 billion, making it one of the costliest natural disasters in the U.S. history.

Unwilling to cede the mantle of leadership to Mr. Obama, Mr. Romney spoke by phone to Deputy FEMA Administrator Richard Serino and officials from the Homeland Security Department and the National Weather Service. Addressing supporters in Iowa, he cautioned, like Obama, that the damage would likely be significant.

In the competition for attention, however, Mr. Obama held the edge. “This is going to be a big storm,” he warned, as cable television broke off to carry his message live. “It’s going to be a difficult storm. The great thing about America is when we go through tough times like this we all pull together.”

But as president, Mr. Obama could bear the responsibility for any missteps in the government response to the storm. Obama advisers say they’ve learned the lessons from President George W. Bush’s widely criticized response to Hurricane Katrina in 2005. Mr. Bush was seen as ineffective and out of touch, and his presidency never recovered.

Aides at Mr. Romney’s campaign headquarters planned to scale back criticism of Mr. Obama to avoid the perception that Mr. Romney was putting politics ahead of public safety.

Mr. Romney, his wife, Ann, and his running mate, Paul Ryan, all planned to attend storm relief events on Tuesday. Mr. Romney was scheduled to be in Ohio, his wife in Wisconsin and Iowa, and Mr. Ryan in Wisconsin all of them battleground states.

Aides said Mr. Romney might visit with storm victims later in the week, much as he did when Hurricane Isaac raked the Gulf Coast during the week of the Republican National Convention.

With the race in its final full week, most national polls showed Mr. Obama and Mr. Romney separated by a statistically insignificant point or two, although some said Mr. Romney had a narrow lead for the overall popular vote.

The election will be won or lost in the nine most competitive states that are not reliably Republican or Democratic. Republicans claimed momentum in these states, but the president’s campaign projected confidence. Mr. Romney’s increasingly narrow focus on Iowa, Wisconsin and Ohio suggested he still searched for a breakthrough in the Midwest to deny Mr. Obama the 270 electoral votes needed for victory.

The U.S. president is not chosen by the nationwide popular vote, but in state-by-state contests that allocate electoral votes. Each state gets one electoral vote for each of its seats in the House of Representatives, as determined by population, and two electoral votes for each of its two senators. That means there are 538 electoral votes, including three for Washington, D.C. The winning candidate must have 50 percent, plus one, or 270 votes.

Mr. Obama is ahead in states and Washington, D.C., representing 237 electoral votes; Mr. Romney has a comfortable lead in states with 191 electoral votes.

Mr. Obama’s team had planned to kick off the final full week of campaigning with a trio of joint rallies with former President Bill Clinton. The two presidents were supposed to spend Monday dashing from Florida to Ohio to Virginia rallying Democratic supporters and trying to sway the small swath of undecided voters.

With Mr. Obama at the White House at least through Tuesday, Mr. Clinton campaigned solo in Florida, then joined with Vice President Joe Biden in Ohio. Mr. Obama’s campaign booked Mr. Clinton into Minnesota, Iowa, Colorado, Ohio, Virginia, New Hampshire and Wisconsin for the race’s final days.

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