The Democrats have been shown to engineer their elections for the past 20+ years. Their problem is that they have at least 2 different camps attempting to do the engineering: the Clinton team and the non-Clinton team. The Clinton team is in it for the self-aggrandizement and to further push off the criminal investigations and prosecutions that should have been taking place since at least 1995. The non-Clinton team doesn't trust the Clintons and desperately wants to keep pushing politics further left (and know they can't trust the Clintons to do so).

I firmly believe the Dems are pushing Sanders to ensure the center point of conversations and debates still remains firmly left of (true) center. They will spring a new candidate next year that seems far more moderate by comparison and settle with the Clinton camp by promising to NOT perform the investigations and prosecutions that Billary so richly deserve.