The thing about Donald Trump is that you can never predict what he'll do. There is now noise about a Sanders-Trump debate. The point for Trump, obviously, is that he wants to brush Clinton aside and treat her as a non-entity. It's a simple dominance game to him. The more interesting thing here is Sanders.
Never before has the nominee for one party had a formal debate with a candidate who lost, past tense, the nomination for the other party. Part of that is that no nominee in history has ever had more chutzpah than Donald Trump, but part of it is that Sanders is approaching some interesting historical territory too. The obvious points of reference are Clinton's 2008 campaign, and Ted Kennedy's 1980 campaign. Let's take the second part first.
If you are a Republican, you remember Ted Kennedy as the guy who killed a woman in a drunk-driving accident and then got away with it because Kennedys are above the law. If you are a Democrat, you are more likely to remember him for this:
Now, that's some powerful oratory. What was going on behind the scenes, though, was that Kennedy never really got on board with Carter. Sorry, I couldn't find the youtube clip of him famously, visibly snubbing Carter, but Kennedy was not what we would call a gracious loser. How much blame does he deserve for Reagan defeating the incumbent that Kennedy only half-heartedly supported in his sulking? Not much, but Reagan probably owed him a fruit basket.
Then there's Hillary Clinton in 2008. She deluded herself into thinking she would get the nomination long after all of the primaries were over. She actually, seriously believed that the "superdelegates" would steal the nomination from Obama on the grounds that he just couldn't win the general election. But eventually she recognized empirical reality, and did far more to unify the party than Ted Kennedy did in 1980.
Now, Sanders is actually toying with the idea of debating the Republican nominee. Could he eventually go the way of Hillary Clinton in 2008? He could, but he is starting to look a lot more like Ted Kennedy in 1980. In a lot of ways. He is the liberal challenger to someone who isn't the incumbent, but is closer to being the formal leader. He is campaigning against someone he sees as too compromised and potentially ineffectual. And his base is similar.
Debating Trump, though, would go way beyond Kennedy in 1980.
Will the debate happen? I doubt it. Right now, most of the Democratic Party is against Sanders, but is trying to treat him with kid gloves so as not to alienate his followers. If he actually did go through with the debate, that would end. The full force of the party would come crashing down on him. With so much opposition from the Democratic Party, the media would be hard-pressed to treat it as anything other than the ridiculous reality show that it would be. Sanders would go the way of Ralph Nader, who went from left-wing hero to the guy who helped Bush 43 get elected. His influence within the party would end.
Then again, anybody trying to predict the twists and turns of this campaign has already been burned so many times that we should never write anything off as an impossibility. So, I'll make sure my popcorn is on-hand, just in case...