U.S. presidential campaigns are never predictable, although the number of late-breaking, surprise developments in the 2016 campaign may set the mark. Here is a historical look at what politicos like to refer to as an "October Surprise" — an unpredictable development that roils the White House race days or weeks before people vote.
But first, a recap on what's happened this year.
Predatory language, groping allegations, sexting and an FBI emails investigation have been the October Surprises that keep on giving.
Early in the month, WikiLeaks, the anti-secrecy organization, 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. Trump dismissed his comments as "locker room talk," but several women have come forward to say Trump made unwanted sexual advances in the past.
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.
Comey's notice to Congress raised more questions than answers just 11 days before Election Day.
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 percent 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 Gov. Chris Christie, R-N.J., and leave Romney struggling to strike the right tone.
Lehman Brothers investment bank filed for the nation's largest bankruptcy on Sept. 15, 2008, setting off a stock market crash and global financial panic that voters largely blamed on the Republicans in power. Republican nominee John McCain didn't help his cause by declaring that "the fundamentals of the economy are strong," a statement mocked by Democrat Barack Obama's campaign.
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 criticizing Bush.
Kerry said he watched the polls freeze and then drop. After the election, Kerry blamed the al-Qaida 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.
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.
This was the case of the October Surprise that never happened.
For a year leading up to the presidential election, Democratic President Jimmy Carter had been trying to secure the release of American hostages in Iran. Critics of Ronald Reagan, the Republican challenger, claim that Reagan's campaign manager and others negotiated privately with the Iranians to ensure that the hostages wouldn't be released just before the election.
Reagan wound up beating Carter, and the 52 hostages were released the same day that Reagan was inaugurated as president. A congressional task force later concluded there was "no credible evidence" of such a deal.
In 1972, as President Richard Nixon was fending off a challenge from Democratic Sen. George McGovern, Nixon authorized national security adviser Henry Kissinger to say "peace is at hand" in Vietnam. The late October pronouncement was welcome news to the war-fatigued United States, and bolstered Nixon's re-election mandate.
It turned out Kissinger's prediction was way off the mark: The heaviest bombing of the war started just before Christmas 1972.
Just days before the election, President Lyndon B. Johnson ordered a halt to all U.S. bombing of North Vietnam, saying he hoped for fruitful peace negotiations. The announcement gave a boost to the campaign of Vice President Hubert Humphrey, the Democratic nominee, but Republican candidate Richard Nixon won the White House.