A last-minute drop out by Clinton benefits Biden most of all. He is an automatic candidate who would be swept in on a wave of sympathy. People like him.
Sanders is unelectable. The right-wing smear machinery propaganda will feed on the word “socialist” and make it synonymous with ISIS. Any electorate that promotes a Donald Trump cannot be persuaded to look at Sanders’ actual policies.
I say this every election. Policies don’t matter. Positions don’t matter. Politicians are like electrons. They exist in a hazy cloud of probabilities rather than a definite position. Voters assign to them a feeling based on where they think the cloud is.
Remember, the OP said in another thread “a leftist president would lead this country to Greece” and “I don’t think the military would survive a Sanders presidency. He would decimate it to pre World War I levels.” This is insanity squared but indicative of what Sanders’ cloud represents to the non-thinking public.
Sanders is greatly useful because he is coalescing a body of progressive opinion that will push the Democratic Party back to the left where it belongs. But he won’t be President.