Mitt Romney and Barack Obama have spent months meticulously planning the endgame of reaching enough wavering voters to eke out an Electoral College victory.

And now it could all be blown away by a monster storm. If Hurricane Sandy does anywhere near as much damage as forecasters are predicting, it will upend both presidential campaigns and leave millions of voters focused more on personal misery than politics.

Oh, and have I mentioned that the media love extreme weather?

The so-called Frankenstorm is expected to make landfall somewhere between Maryland and Rhode Island on Monday, but it is so broad—with tropical storm winds covering 450 miles—that it could wreak devastation along the Eastern Seaboard and as far inland as Ohio.

This is already causing havoc with campaign schedules, forcing Romney and Vice President Biden to cancel weekend rallies in Virginia Beach and Obama to call off events early next week in Virginia and Colorado. The president is heading to Florida on Sunday night, earlier than he had originally planned.

But more than the candidates’ ability to show up in the swing states is at stake. Millions of people may be without power in the final week of the campaign. That means they won’t see the barrage of television ads that the campaigns will be unleashing, despite the fact that Mitt Romney’s team has been hoarding cash for just this moment.

Every analyst says the tight election could turn on get-out-the-vote efforts. But fewer voters might turn out if they’re worried about rotting food in their refrigerators and sleeping in cold houses. The storm could particularly set back early-voting efforts in the affected states.

The situation is reminiscent of the problem Romney faced on the eve of the Republican convention. While Hurricane Isaac turned out to be a bust, just dumping some rain on Tampa, Romney made the right decision in canceling the convention’s first night because the television coverage was all about the storm.

And that, from the campaigns’ point of view, is the killer potential of Sandy. We could be looking at days of saturation coverage on cable news and morning shows, all but obliterating the closing messages that Obama and Romney want to deliver. Even if you live in swing-state Colorado, far from the storm’s path, you’re going to see endless live shots of windswept correspondents in parks getting soaked.

There is one bright spot for Obama, who has been briefed on the storm’s progress by the heads of FEMA, the National Hurricane Center, and the Homeland Security Deparment. If the hurricane is as deadly as everyone expects, he will be able to make news as commander in chief, mobilizing the federal response, and expressing compassion for victims. That might be a better image than that of a candidate repeating the same attack lines on the hustings.

One thing is clear: Mother Nature is about to take over this campaign, and might even affect the outcome.