Ryan planned to leave Ohio at midday for three stops in Florida. His Tuesday schedule, however, shifted him to stops in Colorado instead of Virginia.
The prospect that bad weather could hinder early voting and get-out-the-vote efforts is vexing to both Obama and Romney.
"Obviously, we want unfettered access to the polls, because we think the more people that come out, the better we're going to do," said David Axelrod, a top adviser to Obama's campaign. "To the extent that it makes it harder, that's a source of concern."
In Virginia, one of the most competitive states in the race, election officials eased absentee voting requirements for those affected by the storm.
"The state board of elections is already planning for extended hours in advance for absentee voting, and it's now a priority, moved up to the same level as hospitals and police stations to have power restored," said Gov. Bob McDonnell, a top Romney ally.
Bringing up a safety concern, Virginia Senate candidate Tim Kaine's campaign urged supporters to remove their political yard signs.
"Due to the potential for strong winds in this storm, the last thing we want is for yard signs to become projectiles," said campaign manager Mike Henry.
Getting voters to the polls — whether early or on Election Day — is one of the few elements of the race still in the candidates' control.
Although Romney and Obama are in a close contest for the popular vote, the president continues to have the upper hand in the most contested states.
Reince Priebus, the GOP chairman, pointed to recent gains for Romney that have lifted him to a virtual tie in most national polls.
"The challenger always wins in a tie race," he said.
With time running out, both campaigns appeared to be fine-tuning their map of the states where they're campaigning the hardest.
A senior Republican official, speaking on the condition of anonymity to disclose private deliberations, said Sunday that the Romney team was seriously discussing sending Romney, Ryan or both to Minnesota during the final week.
The state hasn't gone Republican in the presidential race since 1972, but recent polling shows a tighter race there than most anticipated.
In a flashback to the 2008 race, Obama's campaign announced that Biden will campaign Thursday in Pennsylvania, reprising a visit to his hometown of Scranton that he made during the final week four years ago. Pennsylvania, too, has been Democratic territory in recent years, but Romney has continued to contest the state with an advertising assist from the Republican Party.
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