For Nos. 1-4, click here.

5) Iran admits to having nuclear weapons

The dominant issue in the election at the moment is the economy, and it’s an issue the Democrats are winning on, all the way down the ticket to congressional races. Senator McCain’s earlier admission in the primary season that he ‘doesn’t really understand the economy’ and his failure so far to produce a detailed economic plan beyond ‘I’m going to balance the budget and cut taxes,’ hasn’t helped.

Nevertheless, in spite of public feeling towards the war in Iraq and Obama’s trenchant opposition to the war foreign policy is an issue that McCain dominates. It’s partly a question of biography (he’s a POW if you didn’t notice from the 60% of his nomination acceptance speech that mentioned this) but it’s also a question of Senate experience and voters’ traditional confidence in Republicans on issues of security.

If Iran was conclusively found to have nuclear weapons America would be forced to respond. Bush might – West Wing-style – leave the next President with a new war to fight, he might bide his time with economic sanctions, diplomacy, and UN negotiations. Either way, this would be of tremendous help to the Republicans.

Of course, as with a lot of these surprises timing is everything. Should this happen on the eve of the Vice-Presidential debate for example, Biden’s foreign policy expertise will ensure that the debate is car-crash television. The best hope of success for the Republican ticket with this ‘October surprise’ would be it happening before the foreign policy Presidential debate, or near the end of October, so Obama has no time left to dissuade typical voter reactions to security issues.

Would help: Republicans

6) Major breakdown in situation in Iraq

This would really throw open the race, not least because it wouldn’t necessarily automatically benefit either side. On the one hand, McCain has really owned the Iraq issue in the last few weeks and the sudden breakdown in the situation with throw his claims that the ‘surge’ has worked. On the other hand however, it would also throw Obama’s plan to set a timetable for full withdrawal within 16 months. McCain could criticise the Democratic nominee by pointing out that Iraq isn’t stable enough for withdrawal and that the plan to begin handing back power to the Iraqi government has been rushed; but Obama could just as easily suggest that the GOP’s judgement with the ‘surge’ wasn’t all he’s talked it up to be and a reminder of the disastrous state of the Iraq war would surely boost support for the man who opposed it from the start.

Perhaps the ace in the pack here is Senator Biden. While Palin wouldn’t be able to weigh in on the issue without highlighting her complete lack of foreign policy experience, a breakdown in current tactics could well throw fresh support by Biden’s long-touted plan to split the country in three, leaving almost autonomous Kurdish, Sunni and Shiite areas. That could be enough to ensure this surprise would benefit the Democrats.

Would help: Democrats, probably

7) Terrorist attack on US domestic soil

In the same way that a McCain health scare would be game over for the Republicans, a terrorist attack would, in all likelihood,

Slogans of hope and change, and the promise of a fresh young face would, I feel, be wiped out should a terrorist attack take place on US soil, especially if it is linked to Al-Qaeda. In times of vulnerability voters generally become more conservative, they turn to what they know. Expect the familiar face of an experienced, ex-military man with the slogan ‘Country First’ to be irresistible. For many Americans (80% at the current count) President Bush has taken the country in the wrong direction. However, he has nevertheless succeeded in one key respect – he’s kept the country safe since 9/11. Republicans still have a huge edge amongst voters on security issues, and I can’t see Americans being ready to elect a foreign-born, foreign-looking man with the middle name Hussein in the immediate aftermath of a terrorist atrocity, as irrational as that may be.

A failed or foiled attack would have a similar (though weaker) effect of swinging the election to McCain’s favour but would not quite be game over for the Democrats. More likely, and still damaging for the Obama-Biden ticket, would be if the US government were to raise the colour-coded threat level in October as happened in 2004.

Would help: Republicans

The unknown

Of course, the reason politicians fear an ‘October surprise’ is because they’re so-called because they’re not predicted and they’re not planned for.

The biggest game changer of all could be something no-one sees coming. We’ll just have to wait and see.