Washington - Behind the scenes after a US presidential election debate, so-called spin doctors wrestle to impose their own side's interpretations of what the country just heard.

Campaign specialists evaluate and parse every event, comment and speech. Their prime goal is to make an impression on the US media, which are covering the longest and most expensive campaign in US history around the clock on cable television and the internet.

It should come as no surprise that in the fight for the White House, the nominees from both major parties are considered media darlings.

In the Democratic Party primaries, Barack Obama beat rival Hillary Clinton, whose team repeatedly complained about the media's infatuation with the Illinois senator, who hopes to become the first African-American president.

And war hero John McCain, the Republican candidate, has long been regarded as a media favourite for his self-deprecating humour, straightforward style and fondness for dissent, which had often put him at odds with his own party.

The work of the campaign gurus is most evident after the televised debates. As soon as the last question is answered or dodged, each side starts offering its interpretation, even before the candidates finish shaking hands like best friends.

For example, Obama's head strategist David Axelrod tried after the first debate last month to squelch the impressions of many journalists that Obama had been "too nice."

"There were clear differences. He made a very strong case, absolutely," Axelrod insisted.

Steve Schmidt from the McCain campaign tried, in a form of political judo, to use the weight of Obama's own words against him.

"Senator Obama was right tonight when he said John McCain was right, 11 times," Schmidt repeatedly said.

Both sides know that the public judgement is formed not only by the spontaneous impressions of millions of viewers who watched the debate, but at least as much by the tone of the media coverage in the hours and days that follow.

The spin on stories throughout the campaign - and especially the debates - is often decisive.

According to The Washington Post, Obama spokeswoman Linda Douglass was stunned to see how top TV commentators repeated Schmidt's interpretation in their programmes, Obama's 11 times of agreement with McCain becoming something of a cliche in the media in the days that followed, albeit factually true.

In the end, Schmidt's comment was conclusive and easy to verify, even if it in no way reflected Obama's commanding performance in the debate.

"The spin is something we should pay less attention to, but it's important because it can change the story line," NBC's Andrea Mitchell said.

After the second debate between McCain and Obama, held last week, CNN anchor Anderson Cooper derided the "spin room," where partisan commentators make themselves available to journalists looking for quick and easy quotes or instant analysis.

The campaign pitting Obama against McCain is a spectacle of historic proportions, and is often staged as a show. In the final two months of the election battle, the debates are the most important episodes.

It is not just journalists, politicians and experts who are employed to analyze events. Psychologists interpret gestures and body language, linguists evaluate formulations, and focus groups study every sequence of the debates.