The White House doesn’t know:
Q Jay, some of the utilities are saying that the power is going to be out in some areas for up to 10 days, which would obviously include Election Day. Is there any contingency planning to alter the Election Day schedule because of this?
MR. CARNEY: I think that is not something I’m able to address. The fact is the storm is just taking effect now and having an impact now and making landfall I believe tonight. We have to focus on not the campaign and not the election, but on making sure that all federal resources are both prepositioned and in place to help states and localities respond to the storm, to help Americans who are affected by the storm. That’s our focus right now.
Q Would the President have the power to adjust Election Day?
MR. CARNEY: I don’t know the answer to that question. I think you’re getting way ahead of yourself here.
Short answer: No.
Long answer: Hell no.
The president has no authority to alter election day, which is uniformly established under federal law. 3 USC § 1:
The electors of President and Vice President shall be appointed, in each State, on the Tuesday next after the first Monday in November, in every fourth year succeeding every election of a President and Vice President.
States have the authority to set terms for early voting, absentee voting, voting by mail, etc.. But the electors shall be appointed on the first Tuesday in November. Come hell or high water.