For many Americans, the contest between Biden and Trump doesn't just arouse feelings of annoyance or apathy.

This is also a nation where one half of the electorate believes that victory by the other side would spell disaster.

Add to that a precedent of not accepting the result, deep tribal divisions, fake news, a tradition of sporadic political violence plus tens of millions of guns and you have the ingredients for serious unrest.

It is alarming how often even the once unthinkable spectre of civil war has been resurrected from the darkest pages of American history.