I believe that. Many people will not admit to supporting Trump.
However, there is something called a “bandwagon effect”. If this trend continues, especially after the first debate, undecided people are more willing to “jump on the bandwagon.”
I realize many (myself included) believe Biden will not engage in the debates. But even the act of pulling out is going to cause some to decide in Trump’s favor.
True undecideds will be upset with him not debating and as long as the Trump campaign can overcome the spin that somehow it’s Trump’s fault, I think a significant percent (2%?, 3%) will join the Trump Train.
The Biden campaign will surely calculate that the damage of dropping out will be far less than the damage of participating in debates. Unless they rig it with answers provided in advance, no direct talk between candidates, etc so Biden can just read from a prompter the whole time.
A key enabler for that calculation is that the mainstream media can convince everyone that debates don't matter, that they are not historically a thing prior to modern TV era, that Trump is unworthy of debating, etc etc. They will pull out all the stops, and Google / Facebook / Twitter will censor anything that says otherwise. Will that be enough to minimize fallout? I don't know. But Trump can surely make a lot of hay out of it either way.
Agree Biden will NOT debate. I think the decision was made way back that the fallout from him not debating would be less than what would be the utter train wreck if he did.
That's why the bogus polling.