Here's a scenario that might be played out:

The United States delivers a major cyber attack on Russia (Or they conduct airstrikes in Libya) and Russia threatens major retaliation. Obama suspends elections and locks down American cities stating something like Russia has activated it's nuclear arsenal and there's a possibility attacks are imminent so for the safety of the American People he has to declare a state of Emergency and sends troops into the major cities to control any potential rioting and panic that might ensue. It's possible he could use this scenario to his advantage by making up the whole Russian threat or it could be real. Or there is a possibility that Russia might use an EMP in retaliation which would suspend elections indefinitely. Even if no formal announcement of the suspension of elections, people wouldn't vote anyway in the aftermath of an EMP attack...the above scenario has been floating around in my mind for the past few day...just putting it out there.