United Kingdom

They're all fiddling around with their poll weightings after the debacle of the last GE.

By the law of averages, at least one of them's likely to get close to the final result (unless it's a Labour landslide ...). Whether that will result in a repeatable methodology is something only time will tell.

Modelling our multi-party system's a nightmare for polling firms - that and the relatively small number of polls compared to the US's (more or less) two-party setup etc. led to Nate Silver coming a cropper in the last election.