I think Sanders has made a political miscalculation, at least if he hoped to increase his influence with a future Democratic Administration. He should have endorsed Clinton weeks ago if that was the case. Instead he spent the time dithering and Elizabeth Warren stepped into the breach. Since she and Sanders occupy a similar space ideologically and she has such a high media profile, Clinton has turned to her. The credit for unifying the base should have been Sanders and now it will likely go to Warren instead. And whether Warren gets chosen as the running mate or not, she will reap the political benefits of this.
Yeah, Warren as well as Obama. He had maximum leverage on June 7th and it's been gradually declining ever since. He should've started cutting deals immediately.
Of course, Hillary and the Dems aren't going to completely give him the finger since they want him to play nice at the convention and there's nothing to be gained from antagonizing him and his voters, but he's going to get a lot less than he could've gotten had he played his hand better. But then again, that basically perfectly fits his style during his entire political career, so I guess it's only fitting that's the way he goes out too.