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ORLANDO, Fla. - With nine days to the election and the race locked in a dead heat, historic Hurricane Sandy has forced President Obama and Republican nominee Mitt Romney to abruptly change the course of their campaigns and prepare for a potentially devastating storm.

Obama, who flew out of Washington on Sunday night determined to keep a foothold on the campaign trail, cancelled his appearance at a planned morning rally here with former President Bill Clinton to return home to monitor the federal government's response to the storm. He has also cancelled an event planned for Tuesday in Wisconsin to stay in Washington and monitor response to the storm.

"Due to deteriorating weather in the Washington area, the President will no longer attend today's campaign event in Orlando," White House spokesman Jay Carney said in a statement. Officials said they were concerned about deteriorating conditions that could prevent Air Force One from landing.

Romney, meanwhile, plans to keep his campaign at full throttle in three swing states today with stops in Avon Lake, Ohio; Davenport, Iowa; and West Allis, Wis. But the campaign has cancelled events in Virginia and New Hampshire, states expected to be affected by the storm.

His team on Sunday loaded storm-relief supplies onto the Romney campaign bus in Virginia, preparing for deliveries to local storm-relief centers after Sandy hits.

"I know that right now some people in the country are a little nervous about a storm about to hit the coast," Romney said at an Ohio rally on Sunday . "And our thoughts and prayers are with the people who will find themselves in harm's way."

The Obama and Romney campaigns have cancelled or changed 20 events between them due to the storm and safety concerns, sacrificing critical face-time with voters in the home stretch. Obama had also planned to continue today to Youngstown, Ohio, and to northern Virginia, but both events were previously cancelled.

Both campaigns have also halted fundraising e-mails in states in the storm's path.

This "means that, you know, that's going to be putting a little bit more burden on folks in the field, because I'm not going to be able to campaign quite as much over the next couple of days," Obama told Florida volunteers during a visit Sunday night to a field office here.

Obama campaign officials at the Chicago headquarters and in key states in the storm's path told ABC News that while some local canvassing events may be postponed or cancelled over the next few days, they are confident that the situation will not affect early voting or their get-out-the-vote efforts.

"Our historic grassroots organization is running at full speed in Florida and Eastern battleground states to persuade undecided voters and get our supporters out to the polls between now and Election Day," Obama spokesman Adam Fetcher said.

Privately, aides in both campaigns stressed that many key states - Florida, Ohio, Iowa, Colorado, Wisconsin - won't bear the brunt of the storm, if they face any impact at all. In Pennsylvania and New Hampshire, the only early voting is by absentee (mail), so aides said there were no concerns about getting people to polls.

In Virginia, one official noted, the State Board of Elections is now allowing voters who may be affected by the storm to vote absentee in-person.

Political strategists close to both campaigns said Sandy was an "October surprise" whose true impact remains as unpredictable as the outcome of the race itself.

The cancelled events for both candidates does mean the loss of precious time energizing and mobilizing voters and volunteers in a way that only the candidate himself can do. The storm will also surely divert media attention away from the candidates and their messages as they are trying to make their final sell.

However, unanticipated events and big national moments are also an opportunity for candidates to further define themselves and bolster their image as presidential material. Some experts note that by this point in the race it may be difficult to alter voters' impressions.

The latest ABC News/Washington Post tracking poll found Obama and Romney locked in a dead heat at 48 to 48 percent on average since September, the tightest race in a comparable period of the past 76 years. It's also the first contest since 1960 in which neither candidate, in this period, has exceeded 50 percent support.

Obama will spend Monday, Tuesday and Wednesday nights in Washington monitoring the storm and directing federal resources as needed. He is expected to venture to Cincinnati and Akron, Ohio, on Wednesday; and then do a muti-state blitz to round out the week. All of the travel plans are contingent on Sandy.

See Jake Tapper's Good Morning America report on Sandy and the presidential election:

This post has been updated.