The view of the US diplomats was that the sampling formula the opinion poll firms were using was faulty.

“Our election analysis indicates a close race for the presidency. This analysis is based on voter registration data and traditional turnout rates as well as polling on presidential candidate preferences,” the cable says.

“We were concerned that widely published public opinion polls, which showed ODM’s Raila Odinga well ahead of President Kibaki, did not accurately reflect the true status of the contest. Given the rising political temperature, partially due to the use of blatant ethnic appeals by both sides, we were concerned about the reaction of ODM supporters should their candidate lose in a close outcome when they were led by public opinion polls to expect a landslide victory.”

The diplomats argued that the pollsters were wrong to base their sample of interviewees on population alone.

“The Mission quietly reached out to polling firms and their clients to suggest that poll sampling distribution should be based on the regional distribution of registered voters, not on raw population (there are wide variances in voter registration rates around the country, with the high population density areas, such as Kibaki’s native Central Province, enjoying higher rates). Polling on this basis would be a more accurate predictor of the outcome.

“When one polling firm (Consumer Insight) then started limiting its respondents on political preference polls to those who could produce an actual voter identification card, the change was dramatic: Odinga: 41 per cent, Kibaki: 40.6 per cent. Once the Steadman Group re-distributed their sampling according to the August voter registration figures, the Kibaki/Odinga gap shrank from 11 points to 4 points.”