Mr Gore could expose Mr Bush as an 'empty suit' but Mr Bush will try to draw out the colder, harsher Gore

Presidential debates are always significant dates in American election campaigns, but with the race balanced on a knife-edge, this year's debates look especially critical.

Presidential debates have the most impact where the election is close and the candidates are not so well known.

This year both categories apply.

Unscripted moments

There might be plenty of spin afterwards, but debates are one of the few relatively unscripted moments left in presidential politics.

They allow voters to see how candidates respond under pressure and enable them make an informed, in-depth judgement on the candidates unfiltered by the media.

Bush needs to show he can retain his easy-going charm under pressure

Up to half the American population tunes in to at least one of the three debates although this year there has been some consternation that the NBC and FOX TV networks will not be carrying coverage.

Sometimes debates reinforce existing stereotypes of candidates.

In 1992 George Bush famously glanced at his watch when a woman asked him about economic problems, confirming some people's perception that he was out of touch with the problems of ordinary people.

In other cases, debates can be used to neutralise negative stereotypes.

Ronald Reagan managed to make a joke about his advancing years, promising not to exploit his opponent's youth and inexperience, helping to stem concerns that the President was past his best.

So in 2000 George W Bush needs to avoid the kind of gaffes that have led some to think he is not ready for the White House whilst also showing he can talk about substance and retain his easy-going charm.

'Empty suit'

Mr Gore is traditionally seen as wooden and stiff but he is also a powerful debater thanks to his grasp of the issues and brutal, aggressive style, witnessed in his demolition of Democrat challenger Bill Bradley earlier this year.

Gore will be keen to show he is in touch with what matters to ordinary people

An effective performance by Mr Gore could expose his opponent as an 'empty suit' and effectively bury Mr Bush's presidential hopes as the Gore bulldozer mows over him.

The Gore plan will be to bring out differences between the two candidates on core Democratic issues like Social Security and health.

His campaign plan will ensure Mr Bush cannot claim the centre ground whilst also twisting the knife on areas like foreign affairs and leadership where he will hope to show Mr Bush as inexperienced and lacking knowledge.

Neck and neck

On his part Mr Bush will be hoping to do a number of things - primarily to focus on Mr Gore's personality and try to draw out the colder, harsher Gore.

Debate dates

3 October: Boston, Massachusetts 11 October: Winston-Salem, North Carolina 17 October: St Louis, Missouri

He will also seek to make some of the character questions about the vice-president's integrity, past actions and fabrications stick.

At the same time Mr Bush will have to make sure his 'smirk' does not make an appearance, which can lead to a perception of arrogance even though most people think it is rooted in fear.

Mr Gore should do better in the traditional format of this first debate on Tuesday. The second debate, just over a week later, will be more like a chat show which should help Mr Bush.

It is the final debate, in St Louis, Missouri, to be held in the so-called Town Hall format, which is the wild card.

With the polls currently showing the candidates neck-and-neck, the pressure on the candidates will be intense, particularly for Mr Gore who knows that because of the high expectations on him anything other than a victory will be a blow to his candidacy.