Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE's political rise has been the biggest political surprise of the young century.

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But what will be the October surprise in a deeply unpredictable race?

Past elections have been upended with surprise news in October — sometimes from events trigged by the campaigns and sometimes due to factors far out of their control.

In recent elections, unemployment shot up in the weeks ahead of the 2008 race, Osama bin Laden released a video days before the 2004 election and news broke just ahead of the 2000 election that George W. Bush had been arrested for drunk driving decades earlier.

Here are some possible areas that could surprise Trump, Clinton and the electorate this month.

Julian Assange and the DNC emails

Wikileaks’ Julian Assange has promised to release more emails from the massive hack of the Democratic National Committee.

The DNC got a surprise days before the Democratic convention when emails showing DNC staffers tipping the scales in favor of Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE and against Sen. Bernie Sanders Bernie SandersJacobin editor: Primarying Schumer would force him to fight Trump's SCOTUS nominee Trump campaign plays up Biden's skills ahead of Cleveland debate: 'He's actually quite good' Young voters backing Biden by 2:1 margin: poll MORE during the primary were leaked.

The embarrassing disclosures also forced the resignation of former DNC Chair Debbie Wasserman Schultz.

Assange has promised that more is coming, and the Trump campaign has been happy to fan the flames.

Trump informal adviser Roger Stone said this week on Infowars’ “The Alex Jones Show” that a friend is traveling to meet with Assange.

It’s possible an email surprise could also come from the regular releases of Clinton’s official emails by the State Department.

While Republicans have remained untouched by hackers, Trump could also face worries — the hacking magazine 2600 Magazine is offering a $10,000 award in exchange for Trump’s tax returns.

“The October surprise of all October surprises would be getting a glimpse at Donald Trump’s tax returns, whether leaked or hacked,” said Democratic strategist Lis Smith.

“We have no idea what is in his tax returns and there’s all this mystery and speculation built up. It would create a media feeding frenzy.”

Terrorism

The very real possibility of a terrorist attack on the United States would have unforeseen consequences on the race.

Trump has made attacks on the United States a signature point of his campaign, arguing that President Obama and Clinton have been too willing to accept refugees who Trump says could pose a threat to the United States.

Trump’s arguments about the border hinge on economic arguments, but are also focused on security.

During the primary, the San Bernardino and Paris attacks appeared to win more support for Trump’s calls.

Jeff Bechdel, the communications director for the Republican opposition research firm America Rising, said an attack could also damage Clinton’s main selling point, her foreign policy experience.

“Any international incident, terrorism or anything concerning a major power that comes out late in the game I think adversely affects Hillary Clinton,” he said.

“So much of her campaign is tied to continuing Obama’s policies, having the burden of that foreign policy record be part of her own.”

At the same time, Clinton’s central argument is that while she is ready to be president, Trump is not. She also argues that his temperament is unsuited for the White House.

“Every time there’s been an attack or a scare, it seems to help Clinton because she’s a strong, steady hand,” one Democratic strategist said.

“This could be a year where it doesn’t move the needle, or it could reinforce that Sec. Clinton is the steady hand we need.”

Stamina and health

The average age of the two candidates, 69.5 years old, makes this year’s matchup the oldest in American history.

Trump, 70, has repeatedly questioned Clinton’s “stamina,” accusations that Clinton’s team has swatted down as reckless conspiracy theories that have long been floated in conservative circles. Clinton will be 69 by Election Day.

But Clinton’s public stumble at a 9/11 event, later revealed to be caused by dehydration after a pneumonia diagnosis, shook up the race as the two candidates’ health records were put under the magnifying glass.

Any significant revelations about Clintons’ health would play right into that narrative.

“I don’t think they could withstand another incident like that this close to Election Day,” said one GOP strategist. He added that while he’s not expecting another incident, the footage from the 9/11 event was “unsettling.”

A health scare for Trump, who brags about his penchant for fast food and his limited exercise while on the trail, would have a similar effect. But the GOP nominee hasn’t had any public bouts that have drawn concerns like Clinton has.

A Foundation surprise

Both candidates have been dogged by questions about their charitable foundations.

For Clinton, the question is whether foreign donors to the Clinton Foundation won access to the former secretary of State when she was at Foggy Bottom.

Trump has been the subject of a series of damaging stories in The Washington Post about his foundation.

Those reports found that he donated foundation money to the Florida Attorney General weighing an investigation into his Trump University, and that he used foundation money to pay off personal debts as well as a self-portrait, among other things.

The drip-drip of information seems unlikely to end before Election Day. The question is whether any bombshells are still on the way.

Who knows?

The thing about surprises is, they’re a surprise. And there’s no end to the list of unknowns that could crop up this month.

Events completely outside of the candidates’ control could also crop up, such as tragic instances of police killing unarmed black men or others murdering police officers that have been a dark cloud on the year.

The economy could also have an impact on the race if there are unexpected instabilities in global markets.

The surprise could be a new feud or it could be a new scandal.

On the last day of September, reporters awoke to somewhat of a surprise: Trump’s feud with a former Miss Universe had escalated to the point where he had accused the woman of being in a sex tape.

How much of a surprise that was depends on how shocked one has been by the whole unpredictable 2016 race.