It's safe to say by this point that Hillary cannot afford to pick a centrist/center-left running-mate like Tim Kaine, not if she is to have any hope of reconciling with Sanders' supporters (not to mention Bernie himself) and get them energized for November. There's a host of other, more substantive changes that would need to be made to the Democratic Party, but picking a running-mate that could gin up enthusiasm for Hillary would be an excellent start.
This makes sense, but I really don't think the most staunch Sanders supporters will vote Clinton unless she chooses Sanders. Warren and the like will probably not generate enough support amongst those progressives.
