Hurricane Sandy has upended the closely fought presidential campaign, canceling some early voting and disrupting campaign events in battleground states a week before Election Day.

President Obama and Mitt Romney tried to navigate the tricky politics of dealing with the historic storm. It remained unclear which candidate, if either, would benefit, but their somewhat differing responses on Monday gave voters more insight into two men who have offered starkly different visions for America.

Romney, in perhaps the more difficult role, of challenger, struggled slightly to hit a note that sounded presidential while maintaining his apparent momentum in the race: He initially vowed to press ahead with his campaign events but then abruptly canceled most of them for the duration of the storm.

Obama, after touring the battleground states last week and shouting himself hoarse at rallies, pivoted to his role as commander in chief. He canceled an appearance in Orlando with former president Bill Clinton, returned to Washington, convened a storm briefing in the White House situation room and then addressed the nation.

“Obviously, everyone is aware at this point that this is going to be a big and powerful storm,” Obama said. “Millions of people are going to be affected.”

In response to a question about the impact on the election, he said: “Right now, our number one priority is to make sure we are saving lives.’’

On Tuesday, the White House said Obama would stay off the campaign trail for a third consecutive day Wednesday, eschewing planned events in the critical state of Ohio, to continue monitoring the emergency response.

But politics hung in the air, if more discreetly than usual, as both campaigns recalibrated their strategies in a race that had been widely seen as a dead heat but that is now essentially frozen in place until the storm is over — and perhaps beyond. The Obama campaign convened a conference call to say that the president’s victory is inevitable, while Romney aides cited newspaper endorsements of the Republican candidate and evidence of his momentum in Ohio.

Obama aides had expressed concern that getting their supporters to the polls for early voting, a key part of their strategy, could be affected by the storm.

In the Washington region, early voting was suspended in the District and in Maryland. In Virginia, a battleground state, the storm forced the suspension of in-person absentee voting in 26 localities Monday, mostly in the heavily populated Northern Virginia and Hampton Roads regions.

Several of the Virginia locations were open for business on Tuesday. But some of those that remained shuttered were in Northern Virginia, a potential disadvantage for President Obama, who swept the region four years ago and won a sizeable margin in absentee voting. Officials in Maryland said early voting would resume Wednesday, and polling stations would extend their hours and stay open for an additional day to make up for the time lost to the storm.

A few places in North Carolina also closed down early voting because of the storm. But it continued unabated in Ohio, perhaps the biggest prize of all.

Aboard Air Force One on Monday, White House press secretary Jay Carney said he did not know whether Obama had the power to delay the election if there were still widespread power outages next week. But officials in Virginia said the election would proceed, and they announced plans to move polling locations, assuring the public that most voting equipment can operate on batteries.

If power is still out on Election Day, the areas that could be affected include Philadelphia, where Obama urgently needs a strong turnout in a state where Romney has been moving up in the polls, and southwestern Virginia, the most conservative part of the state, which appears primed for a sizable snowstorm.

Even the monthly Bureau of Labor Statistics jobs report, due out Friday and considered important in a campaign that has turned on the economy, could be affected, since the storm closed down some federal agencies. Labor Department spokesman Carl Fillichio said that staffers “are working hard” to get the report out on time.

As the day began, the Romney campaign issued a statement saying the candidate would maintain a full schedule of events Monday in Ohio, Iowa and Wisconsin, and that running mate Rep. Paul Ryan (R-Wis.) would as well.

But later in the morning, the campaign canceled all of Romney’s rallies for Monday night and Tuesday as he was about to begin his first event of the day at a high school in Ohio. Romney’s advisers said they were worried about what one called the “split-screen problem” — live images of him rallying enthusiastic supporters juxtaposed against images of devastation along the Eastern Seaboard.

The storm also disrupted the closing argument Romney had been planning to unveil on Monday with a retooled stump speech focusing on his promise of “real change on Day One.” At a rally in Iowa before his events were canceled, he struck a positive tone on the future of the country and made note of the storm, telling the crowd that “the damage will probably be significant” and urging supporters to donate to the American Red Cross. He added that he had spoken with the National Weather Service and the Federal Emergency Management Agency.

Carney said it was too soon to assess the storm’s impact on the election. But Obama’s top strategists on Monday pressed forward with a story line that victory remains in reach — and, in fact, is inevitable.

The president’s team has “data and facts on our side, versus spin and wishful thinking on theirs,” campaign manager Jim Messina boasted on a conference call with reporters. “What the facts and numbers clearly show is that the president is going to win this election.”

The contrasting approaches to the storm reflected two candidates with differing visions for America who are now trying to juggle the imperatives of responding to a natural disaster.

For Obama, the storm’s challenge is a delicate one: to function as an effective commander in chief while waging a fight for his political life — and to avoid being seen as placing politics over the needs of storm-damaged areas and their residents.

Romney also will need to respond to storm damage but avoid the appearance of exploiting it for political gain.

Volunteers for both Obama and Romney in Virginia said they weren’t especially alarmed by the potential for Sandy to set them back politically; their sense was that the storm’s impact would be neutral, since it would freeze activity for everyone, and that they would resume the frenetic pace once Sandy had passed.

Barbara Kanninen, a volunteer from Arlington County and co-chairwoman of the president’s “Women for Obama” effort in Virginia, said: “I haven’t sensed any frustration on the part of the staff, volunteers or friends. I’m not frustrated, either. Our first priority is everyone’s safety.”

And Christine O’Connor, a Romney volunteer from Arlington, said, “Most Republicans prefer to vote on Election Day, so that’s still good for us. . . . I’m just going to play it by ear to see if we have power.”

Ed O’Keefe and Amy Gardner contributed to this report.