Sociology in the US likely has a significant bias in all polls concerning Trump, just like it was happening before his victory in 2016. Do you remember these highly credentialed experts? Pepperidge Farm remembers.

Those who support him may often consider their position disfavoured by pollsters and thus keep it in secrecy till elections. The same mechanism is skewing all polls in Ukraine, where folks tend to avoid direct answers about whether they prefer peace talks instead of forever war, strongly favoured by Zelensky.

Hence all polls that show tie or slight Harris' gain might better be discussed with such a skewing tendency in mind.