By Richard Downes, Washington Correspondent

The first Presidential debate is one of those key moments in this campaign. Both candidates have been preparing intensively for it.

Mitt Romney has been holed up in various hideaways to hone his skills with Senator Rob Portman, a close associate, playing the role of debate opponent.

President Obama has come to debate preparation late. He has been staying at an exclusive resort near Las Vegas, while his surrogates have tried to play down his chances.

They appear to be saying that he is the underdog in this contest. That is almost certainly stretching the truth to breaking point. Barack Obama is the president and that comes with advantages.

Mitt Romney, as the challenger, has started the campaign at a disadvantage. But the debates have a levelling effect. We will all be watching to see how this works out. Independent commentators have consistently said that Romney has to win and win convincingly to make up the ground he has lost against the incumbent.

That could make for an explosive debate. But others in the Romney campaign have said that this approach could be a mistake and could lead to Romney over reaching himself. He is a stiff character with little of the ease and word-mastery of Obama.

A ‘bull in a china shop’ approach by Romney might not help him. For Obama, success might be more difficult to define. The independent view seems to be that he needs to go back to the ‘No drama, Obama’ mantra. Steady as she goes, would be sufficient for him.

But debates always throw up something unexpected and we will all be watching for those, won’t we?