Hurricane Sandy, the awful October surprise, will not postpone the presidential election. But it will change its inflection significantly. One reason is obvious and optical and everyone has already remarked upon it: It's a real-time test of presidential leadership.
But the other is more significant in a way. The government will have to pass an emergency spending bill during the lame duck session of Congress because cleaning up New York City in particular will require billions of dollars that aren't currently authorized or budgeted for. The looming threat of the sequester cuts has to reckon with the reality of need. President Obama and Democrats will call on Congress to pass aid quickly, and without strings attached. Republicans might not want to do that without offsetting revenue cuts. (The GOP has insisted on such cuts before for emergency spending).
Now, if you're President Obama, you probably schedule a visit to New York City on Wednesday, returning to the campaign trail, probably in New Hampshire, on Thursday. You've got little to gain from leaving your post until order is restored. In fact, you look better if you stay in D.C. It's true that in such a tight election everytime Air Force One touches down in Ohio or Colorado you'll gain votes, but the headlines you'll get if you assume the mantle of leadership right are better. Another benefit: You'll get to rest your voice and brain a bit for the last 72 hours of the campaign, when you'l need all the energy you can muster.
If you're Mitt Romney, you stage a relief event to get a photo op out of it, which is important to have for news coverage. And then you use your campaign list to solicit donations for the Red Cross. And then you return to the trail as soon as possible.