Over the course of the three presidential debates, Barack Obama and John McCain will gradually sink lower and lower. That’s not a comment on what they will say but on their posture. They will do the first debate standing, the second perched on stools and the third sitting down. If there were a fourth they might be lying on loungers with cocktails.

Standing is the least natural, the most staged, of all. Like bad actors, many speakers do not know where to put their hands. The worst among them wave them around at random, as if they were landing a plane or doing contemporary dance.

The only way to look natural, especially on television, is to exaggerate the lift of the shoulders. The same is true, on television, for body language as normal speech: shouting sounds natural and speech sounds timid. Mr McCain needs to stop looking down. Mr Obama needs to reach for the stars but not necessarily look at them.

Perching on a stool is the most difficult of the three stances. There is nowhere to hide, nowhere to conceal notes or aides-mémoires. Honesty and sincerity, especially the fake variety, are conveyed by steady eye contact and leaning towards the audience. This is more difficult when you’re simply trying to get through the debate without falling off.

Sitting down is, at the same time, the most passive and the most aggressive. A great oratorical declamation sounds odd from a man sitting at a table. So the language is likely to be less grand. Franklin D. Roosevelt, no stranger to great speeches, gives the right advice for this series: “Be sincere, be brief, be seated”.

Phil Collins is a former speech writer for Tony Blair

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