(MCT) — WASHINGTON — Hurricane Sandy added an unprecedented dose of uncertainty to an already-unpredictable presidential race Monday, forcing President Barack Obama and Republican Mitt Romney to scramble their campaign schedules and raising the possibility that some states might have to alter Election Day plans.

Obama canceled a campaign appearance in Florida and raced back to the White House, mindful that his performance leading the federal government response could become a major boon or liability to his re-election chances. Romney canceled campaign events for Monday night and Tuesday, and both campaigns curtailed fundraising efforts in states that Sandy was expected to hit.