None of the polls we're hearing about

[Brainstormy]

likely include the newest voters and definitely don't include recently registered voters.
Here is some polling data on the youth vote. It doesn't look good for Trump. I think there will be some surprises in store for the GOP.
https://www.washingtonpost.com/opinions/2023/07/25/voters-progressive-trump-harvard-youth-poll-gop/

[brooklynite]

1. On what basis do you make that assertion?

Because a poll that you DO like says something different?

nb: every poll includes cross tabs by age if you want to get into the weeds.

[Brainstormy]

2. Mainly because they don't have the data yet.

it's not that they couldn't declare their age. It's that they're not getting polled.

[brooklynite]

3. That is also a supposition.

There seems to be a contingent of people who don't work in polling who are convinced that it's not possible to conduct accurate polling. If that was the case, candidates wouldn't be paying for polls.