Contrary to popular beliefs US presidential debates don't appear to have much impact on the polls despite the retroactive importance placed upon them. What usually happens is that whichever candidate wins has some moment in the debate retroactively turned into a campaign winning one liner. In the absence of debates our media attribute random poll fluctuations to other events.
I feel confident in predicting that unless one of the candidates appears on stage in a nappy flinging his own faeces there will be no noticeable difference in the first batch of post-election polls that in the last batch of pre-election polls.
Even John le Carré would have difficulty telling this tale
25 minutes ago