“How will Joe Biden fend off Bernie Sanders?”
It’s all about timing. The Administration will hold off any indictment until at least a couple weeks after the convention is over. This way, Bernie-mania will be considered “over”, and they will bring in the emergency white knight Biden to save the day.
I believe at this point this is a very plausible scenario. If the Administration thinks HRC is toxic and can’t win, no way will they take their chances with her against Trump. The Dems don’t operate that way — they play to win.
Now whether Biden can beat Trump is another matter entirely. Biden provides a target-rich environment for Trump to make fun of. But at this point, he’s probably the best hope for the Dems.
Subbing Biden may push Sanders into running as an independent. Biden will pull less votes than Hillary. He’s not a woman and he’s not black.