President Barack Obama left the campaign trail to lead his nation at a moment of crisis, steering the response to super storm Sandy, which left the endgame of the White House race in turmoil.

Republican Mitt Romney joined the president in cancelling campaign appearances as high winds, swamping tides and lashing rain hit the northeastern United States and conjured a moment of political peril for the rivals.

Coming so close to the neck-and-neck election on November 6, the potentially historic storm threw closely planned campaign strategies into disarray, could dampen early voting, and may drown out the candidates' closing arguments.

"This is going to be a big and powerful storm," Obama warned after meeting disaster and emergency officials at the White House, and ditching events in battlegrounds Florida, Ohio and Virginia and rushing back to Washington.

"The great thing about America is, when we go through tough times like this, we all pull together," Obama said, projecting authority as he grabbed headlines in a televised statement.

"The election will take care of itself next week. Right now, our number one priority is to make sure that we are saving lives."

Romney cancelled events Monday evening and on Tuesday as a mark of sensitivity towards millions in the path of the storm, but went ahead with scheduled appearances in Iowa and Ohio.

He was also briefed by the deputy administrator of the Federal Emergency Management Agency, Richard Serino, on the storm relief effort, aides said.

"The damage will probably be significant, and of course a lot of people will be out of power for a long time," Romney said in Iowa.

"Hopefully your thoughts and prayers will join with mine and people across the country as you think about those folks who are in harm's way."

"We love our fellow Americans -- wish them well," he said, and appealed for supporters to make donations to the Red Cross.

Romney must balance a desire to use the precious last days of the campaign to maintain momentum, with a desire to avoid appearing oblivious to suffering Americans.

He has already been accused of muscling in on tragedy for political gain -- over the attack on the US consulate in Benghazi last month -- and so can ill afford any missteps seen as motivated by a hope of an electoral dividend.

Equally, any errors by Obama in the wake of the storm could help Romney build his case that Benghazi was a symptom of a wider malaise and unraveling of leadership in the White House.

Top US office holders have been acutely aware of the potential of disasters to wreak a political price ever since president George W. Bush's bungled handling of Hurricane Katrina seven years ago.

High-level campaign operatives deplore events they cannot control, hence the fabled history of the "October Surprise" -- the sudden happening, at home or abroad, with the potential to reshape the late stages of an election.

For Romney, there is political danger in being seen as an afterthought as Obama shapes the narrative of the post-storm response, possibly squelching a head of steam the Republican has built up in recent weeks.

FEMA chief Craig Fugate was quoted as saying by Politico that there could be "impacts" on the election next week, but left exact arrangements up to states.

The storm and likely widespread power cuts in swing states like Virginia will also disarm plans by both campaigns to deluge voters with non-stop television advertising in the final days.

The storm could also dampen early voting turnout, even in places as sheltered as midwestern Ohio or battleground New Hampshire, on which the Obama campaign is counting.

The normal election back and forth did take place at a lower intensity Monday.

Romney warned America faced a "critical time" of "enormous challenges" and slammed Obama for believing that the country was "on the right track" as he posed as an agent of change.

The Obama campaign hit back at Romney's claim that Chrysler planned to move production of Jeep vehicles to China, which the company has already denied, through former president Bill Clinton.

"They put out a statement today saying that it was the biggest load of bull in the world that they would consider shutting down their American operation," Clinton said.

Obama's campaign warned reporters not to fall prey to Romney's "spin," insisting that the president was ahead.

"We are winning this race," said Obama's senior aide David Axelrod.

"We base it on cold, hard data based on who has voted so far and on state-by-state polling."

In a memo however, Romney's Ohio state director Scott Jennings said the president was facing a "nightmare" scenario in the key state.

Romney leads by a few points in some national polls of the popular vote, but Obama is clinging to a slim advantage in the state-by-state race to 270 electoral votes needed to secure the White House.

But Obama was up one point, a swing back to the president of three points from last week, in the latest GWU/Politico/Battleground poll Monday.

A CNN/ORC poll in Florida, the biggest swing state, meanwhile suggested the race there has tightened, with Romney leading by only a single point.

[Image via Agence France-Presse]