He's so full of ****. This is about his pride. Since he cant win the nomination he's gonna drag this thing out until the bitter end. Hillary needs to pivot to the general election and get started on Trump before the convention. Not spend the next 2 months waiting on this old selfish fart to **** off.
I think as long as he tones down the rhetoric about Hillary and stick on the issues, I have no problem with him staying just to gain a little voice.