When do you think?
Depends on how many days it’s got rolling if it’s a 7 day average and the poll has been fairly stable for the past week it would take a 7 point swing in one day to manifest as a 1 point swing.
If a measurable move has happened and the poll is a rolling average, unless it was a massive shift, will take a few days to start to really manifest.
In a 7 day rolling average poll, you won’t know the effect of a specific event until it has rolled off the average. If the poll had moved significantly today, it could have been just as easily a significant day rolling off the average as a significant day rolling on. So the best answer for figuring out if the last debate had any real impact is to wait until next Wednesday.