John Robb claims that conditions are such that in November civil war engulfs this country via the actions of just five people:
One candidate declares victory. The other cries foul. Protests go national. Violence, looting and active engagement with police.
Calls for calm ignored. Martial law is declared in different areas. Internet is turned off in different areas.
Violence grows. The global economy collapses due to uncertainty over US economy (ill conceived financial derivatives ensure that virulent US contagion spreads to every nook and cranny of the global financial and economic system).
The US, suddenly impoverished, extremely angry, and mortally betrayed stumbles into civil war.
Read his blog post for the details of how it might be done.