ST. PAUL, Minn. -- An election-eve terrorist strike. A tanking stock market. A stunner of a jobs report. An unscripted moment.
Democratic President Barack Obama and Republican rival Mitt Romney are on guard for anything that could push the presidential race from its taut course. An autumn surprise is just that, making most late-breaking events tough to plan for.
"You can't overestimate how much the campaigns are sort of on autopilot. In some ways they're incredibly brain dead. They've got a plan and they are now going to execute it," said Carter Eskew, a top strategist for Democrat Al Gore during a 2000 campaign that came up just short. "They basically trust that they have the system in place to deal with a crisis as best they can."
With less than two weeks of campaigning left, the views of many voters are hardened, judging by many public opinion surveys. The unprecedented millions of dollars in advertising from every corner can drown out or diminish the off-script stuff. There also are doubts about whether any surprise will carry much potency now that millions of Americans cast their ballots days or weeks before Election Day.
Not that either man's supporters aren't trying to knock the other side off course.
In the nine states both campaigns are fiercely contesting, the outcome will be decided at the margins.
Late twists in a campaign take on many forms: a verbal stumble that reinforces an existing weak point, a brewing scandal where the murkiness can be as bad as the allegation, a foreign policy crisis few saw coming. Old scars can face fresh examination. Purported bombshells can turn out to be duds.
So the candidates need to be ready for anything.
A look at some possible events that could shake up the race.
As numbers go, keep one eye on the polls and the other on the Dow.
The stock market is naturally volatile, but big swings have been known to alter races. Four years ago, a skidding Dow Jones Industrial Average caused widespread panic about a seizing economy and proved damaging to GOP nominee John McCain, whose party held the White House at the time. On one September day alone, the index fell 778 points for a drop in market value of more than $1 trillion. Three more steep drops followed in October.
In the past couple of weeks, concern about a fragile U.S. recovery and worries about economic conditions in Europe sent the markets down noticeably.
The Dow closed just below 8,000 on Obama's Inauguration Day, Jan. 20, 2009. It now tops 13,000.
Romney has pinned his campaign on the idea that Obama has failed to fix the economy and left too many people without work.
Throughout Obama's term, a high unemployment rate and joblessness caused plenty of consternation. He finally caught some good news in October, when the unemployment rate dropped to 7.8 percent _ below 8 percent for the first time in his presidency _ as employers added 114,000 the month before.
The last jobs report before the election will be released Nov. 2, a week from Friday.
Democrats worry that even a small tick upward would have a psychological impact on fence-sitting voters anxious for clues about where the country is headed. Another notable drop in the rate could take steam out of Romney's argument.
Economists and investors are already warning of a slowdown in Europe and Asia and that matters because, in an interconnected world, U.S. companies could retract if their business prospects outside the U.S. look weak.
Europe has been a major source of problems, with several countries adopting harsh austerity measures or requiring massive loans to keep economic disaster at bay. A loan default here or a violent protest there could send shudders across the Atlantic Ocean.
Plenty of sensitive overseas situations could test American resolve _ and the incumbent especially _ in the days before Nov. 6.
There's the unrest in Syria, where uprisings have provoked a violent response from the regime. Activists say more than 34,000 people have been killed in the last 20 months. Neither Obama nor Romney is calling for U.S. military intervention. But a small contingent of U.S. special forces is stationed at the border between Jordan and Syria, and any spillover violence that draws them in could cause war-weary Americans to take notice.
Iran's unpredictability in the region also has foreign leaders on edge. Any sign of aggression, particularly against U.S. ally Israel, would make an already delicate situation even more so.
Nuclear-armed North Korea is another constant source of concern.
Who would have guessed that Libya would turn into such a fall flashpoint?
But the Sept. 11 killing of four Americans, including U.S. Ambassador Chris Stevens, served as a stark reminder that the long fight against terrorism is far from over.
Late in the 2004 race, Osama bin Laden released a video threatening more attacks on the United States. It caused some clenching by the electorate, with many late-breaking voters deciding to stick with Republican President George W. Bush and a terror policy they knew. Democratic nominee John Kerry later conceded the video altered the dynamics of the final week of the race.
GUILT BY ASSOCIATION
As much as Obama and Romney mind their own camps, they're also at the mercy of others, to a degree.
Consider the dustup over Republican Indiana Senate candidate Richard Mourdock's remarks on rape and abortion. It put Romney on the spot because he had endorsed Mourdock and cut an ad for him, giving Democrats a new opening to criticize Romney and his party on women's issues.
Obama has been weighed down at times by his former spiritual adviser's charged rhetoric. Republicans also have tried to tar the president by highlighting companies that went bankrupt after receiving millions in federal stimulus money.
Forecasters were watching a powerful storm headed toward Florida and the East Coast that could bring heavy rain, snow and flooding to several states.
The Obama administration's response would be heavily scrutinized and candidate travel to Florida and other states could be disrupted.
The race already has been affected by one storm: the Republican National Convention in August was shortened by a day as a tropical storm bore down on Florida, Mississippi and Alabama.