When the polls show him to be ahead, it's evidence that the voters love him. When he's behind, it's evidence that the polling is rigged.
Campaigns also conduct their own internal polling which may or may not have biases, but they're not released; they're used for the campaign. So it only benefits them to know what's actually going on. Trump's is one of the few campaigns that seems only interested in good news, and in not learning from what their internal polling tells them.
That said, of course all campaigns will selectively brag about the polls that make them look good, and quietly ignore those that don't.
Again, the polls are extremely reliable in this country. If you can't see that, you're unlikely to be swayed by yet another data point when this election is complete.
1. They're the best data we have
2. We have no reason to believe they're incorrect
3. There is REALLY no reason to believe they're dishonest
Is 100% intellectually dishonest.
This is exactly what happened 4 years ago, and apparently some people have not learned from their tremendous mistake.
If you want to know why "turnout at a campaign event" is a crappier metric than "real actual scientific data", I don't know how else to help, other than to point to other instances in which it has failed:
"Mitt drawing larger crowds" http://www.politico.com/story/2012/10/mitt-drawing-larger-cr...
"Donald Trump continues to draw YUGE crowds. That matters less than he thinks." https://www.washingtonpost.com/news/the-fix/wp/2016/09/28/do...
"Trump brags about crowd size but will it turn into votes?" http://bigstory.ap.org/article/d74fbd472f7a420a90737e55cfb20...
I do not know or care who you support in the Presidential election. However, I suggest you get realistic about your metrics, as you're way off in fantasyland at the moment, as far as I can tell.
If you turn out to be incorrect, I hope you learn from this experience. I know I will, if the data turns out to be wrong.