You're delusional, if you think that there is any realistic chance of that happening.
For all his faults, Mr. Trump was elected President specifically because he was seen as the only viable alternative that we were given to a less extreme version of what Sanders represents.
Bernie Sanders has no realistic chance, whatsoever, of being elected President of this country. Even his fellow Democrats know this, hence all the skulduggery in which they are engaging to make sure that he doesn't get the nomination.
Polls show that Bernie is performing as well against Trump as any other Democrat. Better, in fact.
And the Dow dropped 3600 points this week. The argument for Trump's behavior has been, "Well, at least the economy is good". Well, now, the economy isn't going to be that good going forward, so what else you got?
Trump wasn't elected. He lost by 3 million votes. He was selected by an 18th century anachronism.
The main reason why you should be worried... Bernie has a very dedicated group of followers... and that's often enough to flip an election.