WASHINGTON — The October surprise goes by the name Sandy.
And unlike many late-breaking developments of U.S. presidential elections past, neither side is certain which candidate, if either, will be helped or hurt.
What's clear for both President Obama and his Republican challenger Mitt Romney is that the superstorm brewing off the East Coast is shaking up an already hard-to-predict contest as it enters its pivotal final week, upending campaign schedules and interfering with the rivals' ability to communicate with voters as they make their closing arguments.
As they scrapped visits to storm-threatened states, Obama and Romney fanned out to other politically competitive, vote-rich areas — the president to Florida and the Republican contender to Ohio — to begin making their last public pushes, while advisers fretted about the weather's potential impact on their bids.
Members of both parties said there was no way to predict the political effects on either side. Sen. Mark Warner, D-Va., said the weather would "throw havoc" into the race, and Republican pollster Whit Ayres said it might be enough to change its course.
"Anything could be significant in races that are this tight," said Ayres, who isn't affiliated with either campaign.
Hurricane Sandy is on track to hit the Eastern seaboard later Monday and merge with two strong winter storms to create what federal officials called a potentially life-threatening hybrid superstorm. The system will affect four politically competitive states — New Hampshire, North Carolina, Ohio and Virginia — denying control by the candidates over the carefully choreographed final days of their campaigns.
Other than Florida and North Carolina, the swing states with the greatest tradition and volume of early voting aren't along the East Coast, so it was unlikely the storm would hamper pre-Election Day ballot-casting.
Still, there was the potential for power outages that could effectively bring about a campaign advertising blackout in Virginia, and a chance that heavy media coverage could drown out both candidates' final messages as voters turn their attention to a major storm, even in states that aren't directly affected.
There were risks and opportunities for Obama, who could benefit from playing the high-profile role of crisis manager-in- chief yet could also be held responsible should the federal response to the storm fall short. He also must strike a tricky balance between governing and campaigning at the most volatile moment in the race.
"This is the challenge of being the president and a candidate," said David Axelrod, the campaign's chief political strategist. "Being the president comes first. We as a campaign will make the adjustments as necessary and he'll do what he needs to do as president."
That meant Obama scrapping an event that had been scheduled for Monday in Youngstown, Ohio — a day after he had canceled Sunday's planned appearances in Virginia — so he could return to Washington to monitor the storm. Obama received a briefing from federal disaster relief officials Sunday and spoke by telephone with mayors and governors who may be affected, before leaving for Orlando, Fla., for an event Monday morning.
"We have to take this seriously," Obama said of what he called "a serious and big storm."
"My first priority has to be to make sure that everything is in place to help families and to prepare," Obama said later at a field office in Orlando Sunday night. Delivering pizzas to campaign volunteers, he said the storm could impede his ability to make the final push for a second term in person.
"I got to get back to D.C. because the storm is sweeping into the mid-Atlantic," he said. "That's going to be putting a little more burden on folks in the field."
Romney, who also scuttled Virginia events Sunday and headed for Ohio, canceled a visit scheduled for Tuesday in New Hampshire. Instead, he will hold an event in Des Moines, Iowa.
"I know some people are nervous about a storm about to hit the coast, and our thoughts and prayers are with people in harm's way," Romney told voters in Findlay, Ohio.
Members of his campaign staff were monitoring the storm's progress from campaign headquarters in Boston, keeping in touch with officials and supporters in the most- heavily affected areas. Romney plans to campaign Monday in Wisconsin and Ohio.
"The schedule we have locked in now are in states not impacted by the storm," said Madden.
Both campaigns said they were suspending fundraising appeals in four states that are being hit — Virginia, Pennsylvania, New Jersey and North Carolina — as well as Washington, D.C., though they are still running ads in those areas.
Officials on both sides said it was a challenge, this late in the campaign, to loosen up on schedules that had been planned down to the tiniest detail to maximize voter outreach and boost turnout. For Obama in particular, there's an advantage in a tight race for the president to be on the ground to excite supporters and boost turnout, getting local press coverage and generating buzz.
As Obama's campaign aides held conference calls and traded e-mails over the weekend to map out different storm scenarios, they risked canceling events they might not have needed to, or sticking with visits that ultimately should have been scrapped.
"The big unknowns are the severity of the storm and how the president's response to it will be perceived," said Barry Burden, a political science professor at the University of Wisconsin in Madison. "Obama is in the difficult position of needing to continue the campaign while also acting as the chief executive; that could hurt his re-election chances, or boost them."
Romney's aides said they had no idea how the storm would affect the race. They are preparing for the campaign to effectively grind to a halt in hard-hit areas and are most worried about the effect in Virginia. At the same time, there are limits to the steps they can take right now.
"There are certain things we can't control and nature is one of them," said campaign spokesman Kevin Madden. "So we focus on what we can control."
Madden declined to discuss how the storm might affect the race, saying the campaign's concern is for the well-being of those affected.
"The safety of people that are in harm's way — making sure they get the information they need, the help they need — that's the top priority," Madden said.
In Virginia, Romney's aides said, campaign offices have shifted some of their focus to helping with relief efforts, spending the next few days collecting supplies to be delivered to relief centers after the storm hits.
A crisis gives the incumbent an opportunity to appear "presidential," said Tom Davis, a former Republican U.S. representative from Virginia.
"As an incumbent, you're always looking for a storm, or some crisis, to turn to your advantage," he said. "But I don't think in this case that you're going to see a lot of difference because the areas that may get hit the hardest, in the Northeast, are not really in play."
As for the crucial question of what the storm might do to affect turnout in Virginia, Davis said, "We don't know the answer to that."
Ayres said while any development in a race as tight as the presidential contest may be consequential, there's a greater chance that a predictable event later this week will have an effect.
"The last jobs report coming out the Friday before the election is likely to be more significant than the political implications of a large storm," he said.
That didn't make it any easier for candidates on the ballot to balance appealing to voters with bracing for the storm.
"Thanks for your support," Democratic Senate candidate Tim Kaine posted on the social media site Twitter last night, "but please take down your yard signs so they don't become projectiles." He categorized the message with the hashtag #Sandy.