What if? There's still time for drama before Election Day

[...] both Clinton and Republican rival Donald Trump know there are countless ways the trajectory of this uncommonly volatile presidential campaign still could shift in unexpected ways.

In September 2012, a secretly recorded video emerged that caught the Republican nominee saying 47 percent of Americans pay no taxes and consider themselves victims, feeding into impressions that Romney wasn't looking out for ordinary people.

In October, Hurricane Sandy roared up the East Coast, giving President Barack Obama a chance to showcase his commander-in-chief credentials and leaving Romney struggling to strike the right tone.

Republicans said the release of 24-year-old information at such a time was a Democratic dirty trick, and a Democratic activist acknowledged he had tipped off reporters.

Bush won anyway, but many of his advisers still think the news depressed turnout among social conservatives to make the race much closer than it would have been otherwise, says Dan Schnur, director of the University of Southern California's political institute and a veteran of John McCain's 2000 presidential campaign.

Kerry believes the al-Qaida leader cost him the presidency by issuing a videotape that criticized Bush and warned U.S. voters that "your security is in your own hands" in the election.