In a conference call with reporters on Monday morning, bosses at the campaign headquarters of Barack Obama in Chicago stressed that the president is focused "on the storm and governing the country", and noted that he had cancelled events in storm-hit states from Florida to Wisconsin. A well-handled disaster can strengthen an incumbent president (just as a Katrina-level bungle is a political, as well as human disaster).

Mitt Romney cancelled events planned for Monday night and Tuesday, citing the need to avoid putting supporters in danger or tying up emergency services. In Virginia, the Romney campaign bus will be delivering storm-relief supplies. The Romney campaign also sent out a notice that it had suspended fundraising emails to the District of Columbia, Maryland, New Jersey, New York, North Carolina, Pennsylvania and Virginia.

To be brutal, a certain amount of bad weather on election day helps conservatives in every democracy. In crude terms, car-driving conservative retirees still turn out in driving rain, when bus-taking lower-income workers just back from a night shift are more likely to give rain-soaked polls a miss. School closures are a particular problem for low-income families or single mothers scrambling to find childcare. In this case, the weather is supposed to clear up well ahead of election day, but the impact could be felt in the turnout of early voters.

Democrats will perceive that as bad news. The Obama campaign has pinned big hopes on increasing turnout among Obama-supporting "sporadic voters", the sort of voters who give mid-term elections a miss but may turn out in presidential years. According to Michael McDonald, an elections expert at George Mason University whom I spoke to last week, this is the precise moment in the election cycle when sporadic voters are most likely to turn out.

The very first early voters are those who cannot wait to vote: they are the partisans who could be seen queuing outside polling stations in Ohio or Florida on the first mornings of early voting, like bargain-hunters hitting the sales. Now, several days into early voting and a week from election day, would normally be the moment when less zealous supporters were supposed to be finding a moment to cast a ballot.

There are others who believe that Sandy will benefit the president, with the storm freezing the election campaign, and Mr Romney's perceived momentum, in place. In short, nobody knows how it will impact the race.

For proof of the uncertainty that reigns just now, I can only cite my favourite campaign email of the last 24 hours, a four-paragraph missive from Mr Romney in which one full paragraph is devoted to asking supporters to bring campaign yard signs indoors before the storm strikes. "In high winds they can be dangerous, and cause damage to homes and property," Mr Romney urges.

Sensible advice, no doubt, but something in me likes the idea of a multi-billion dollar election juggernaut being halted by visions of a voter impaled then pinned to a wind-lashed lawn by a flying Romney-for-president yard sign.