Groping, sexting and emails - US 2016 Presidential election's October Surprise

Democratic presidential candidate Hillary Clinton waves to people outside after speaking at a rally in Wilton Manors, Florida. Photo / AP

US presidential campaigns are never predictable, although the number of late-breaking, surprise developments in the 2016 campaign may set the mark.

A historical look at what politicos like to refer to as an "October Surprise" - an unpredictable development that roils the White House race and comes days or weeks, or even earlier than October, before people vote.

2016:

Predatory language, groping allegations, sexting and an FBI emails investigation. It's been the October Surprise that keeps on giving.

Early in the month, WikiLeaks began releasing thousands of hacked emails of Hillary Clinton's campaign chairman, John Podesta. The emails exposed campaign infighting and raised ethical questions about her family's charitable foundation.

The emails would have driven news coverage entirely if not for the Access Hollywood recording in which Donald Trump bragged to TV host Billy Bush about sexually assaulting women.

Then came Anthony Weiner. The former New York congressman and estranged husband of Clinton aide Huma Abedin had already been disgraced in a string of sexting scandals. But when the FBI opened an investigation into his alleged communications with a 15-year-old girl, the bureau discovered emails that Director James Comey said appeared "pertinent" to a previously closed investigation into Clinton's use of a private email server.Trump dismissed his comments as "locker room talk," but several women have come forward to say Trump made unwanted sexual advances in the past.

Comey's notice to Congress raised more questions than answers just 11 days before Election Day.

2012:

In September, as the race between Republican Mitt Romney and Democratic incumbent Barack Obama was drawing to a close, a secretly recorded video emerged that caught Romney saying 47 per cent of Americans pay no taxes and consider themselves as victims.

The comment fed into an existing impression by many voters that Romney wasn't looking out for ordinary people.

Then in late October, Hurricane Sandy devastated the East Coast, giving Obama a chance to showcase his chief executive credentials, get an appreciative response from Governor Chris Christie, and leave Romney struggling to strike the right tone.

2004:

Democrat John Kerry headed into the final weekend of the campaign feeling good about his chances of beating President George W. Bush.

Then Osama bin Laden released a video lauding the 9/11 attacks and criticising Bush.

Kerry said he watched the polls freeze and then drop.

After the election, Kerry blamed the al-Qaeda leader for costing him the presidency. Kerry's theory was that bin Laden's comment had agitated voters. "It changed the entire dynamic of the last five days," Kerry said.

2000:

Five days before the election, word surfaced that Bush had been arrested on a misdemeanor drunken driving charge in 1976.

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 thought the news depressed turnout among social conservatives and made the race much closer than it would have been otherwise.