Aboard Air Force One en route to New Hampshire on Saturday, Mr. Obama held a conference call with Craig Fugate, the head of the Federal Emergency Management Agency, and other top officials to get an update on Sandy. The day before, Mr. Obama had directed Mr. Fugate “to ensure that all available federal resources are being brought to bear to support state and local responders in potentially affected areas along the eastern seaboard,” the White House said in an e-mail to reporters.

The storm could hold repercussions for both Mr. Obama and Mr. Romney, particularly if it inhibits voter turnout in crucial states. In Ohio in particular, the Obama campaign has been counting on its field operation to urge people to vote early, with buses taking voters to the polls after Obama rallies in the state. Republicans, for their part, have been pushing their own early-vote efforts in Virginia, hoping that Mr. Romney can get a head start in vote tallies there.

Josh Earnest, a White House spokesman, said that beyond Mr. Obama’s early departure for Florida on Sunday, there were no plans for additional weather-related changes to Mr. Obama’s campaign schedule. But the president was supposed to campaign in Virginia on Monday; if Sandy is pushing through the Commonwealth at the same time, it is hard to imagine that the president would fly into the storm — or ask supporters to show up at a rally amid heavy winds and rain.

Asked if the Obama team was worried that Mr. Romney could politicize the government response to the storm, Mr. Earnest said: “I don’t want to predict what Governor Romney may or may not say — he certainly does have an interesting track record on this.”

In the meantime, Mr. Obama was trying to make all he could out of the last decent weather day before Sandy was to hit the American mainland. Before heading to the rally in Nashua, he stopped at a local Teamsters office in Manchester to encourage campaign volunteers.