You’re wrong . Americans don’t know who Sanders is or even what socialism means. The media will brainwash and Trick Americans into thinking Sanders is something good for America like the media did with Obama another unknown. Hillary is known so the media can’t do that with Hillary. the media can’t take the establishment label off of Hillary. people don’t want clintons nor bushes.
There are a bunch of ways Trump could make sure the debate never happens without actually being seen as the one who backed out. I think that is the most likely scenario, because Trump has already received most of the benefit he is likely to receive - just by accepting the challenge, he has gotten a bunch of PR, people trying to figure out just how clever he is, he marginalizes Clinton, offers to raise money for women’s health, makes the point again that he can draw ratings and dictate terms to the media. Looks fearless. All that without even setting foot on the debate stage.
If he does actually do the debate, I’m almost positive he will be extremely nice and flatter Bernie, even when Bernie attacks Trump viciously (which he will). Trump knows there are a bunch of #neverHillary type Bernie supporters watching who will vote for Trump or stay home and who would not want to see their guy get trounced, so Trump won’t try.
Instead of fighting back he’ll ignore any attacks and insults and sympathize with him about various things - the super delegates are rigged against him, Hillary is under the control of her big banker donors, etc. Lobbyists and corrupt corporations control DC, etc, etc. The closest Trump will get to a criticism of Bernie would be to say he should have hit her on the email scandal.
Trump also has the option of coming right out and saying “I am not here to fight with Senator Sanders, I just did this to make Hillary look bad”. Everyone will laugh and by doing that he would basically be ‘throwing’ the debate and thus inoculate himself against the media saying he lost.
There are so many ways Trump can work this to his advantage, and I’m sure he’ll do just that.
It’s what he does.