Stopping Sanders isn't the problem; the DNC has all sorts of options to do that. The real problem is doing so in a way that doesn't disaffect a significant portion of Sanders supporters, thereby causing the formation of a viable and independent left-populist movement.
That requires subtlety and confusion. But it can be done.
Remember that superdelegates have only been disenfranchised for the first ballot at the convention. If that ballot doesn't produce a clear winner, superdelegates vote in all succeeding ballots - which means that the DNC is completely in charge.
Given the number of candidates (the vast majority of them corporate Democrats of one flavor or another), avoiding a clear winner in the first ballot will be relatively easy. But even so, it's necessary for the DNC to be cautious. If they're blatant in fixing the nomination, the backlash could be strong enough to cripple the party permanently. That could mean the end of big donations, which must not be allowed to happen.
So the most likely scenario is this: There's no winner in the first ballot. Before the second ballot (or possibly even before the first one), the corporate candidates pool their delegates behind a single choice, probably the one with the highest total to begin with. That's most likely to be Harris or Booker, but my money would be on Harris. Pete Buttigieg might be handed the VP spot, which would explain why he's been part of the "Stop Sanders" DNC lunches that the New York Times recently uncovered.
With the support of the superdelegates, the anointed corporate candidate will be crowned. Sanders isn't likely to object; a threat to his Senatorial committee positions would be sufficient to force his cooperation, as it did in 2016. Angry Sanders supporters will be reviled as sexists (assuming it's Harris), racists, homophobes (thanks to Buttigieg), and sore losers. Meanwhile the DNC will eventually announce that they will convene another committee after the election which will fix the superdelegate rules (again). David Brock's online operatives will buy out, take over, or otherwise destroy online centers of pro-Sanders activists, as they did in 2016.
Of course, the outcome is a likely win for Trump. But that's an acceptable outcome for the DNC. Their primary purpose (no pun intended) isn't to win the Presidency. It's to keep the left from splitting off from the Democratic Party and becoming a viable alternative to the two-party duopoly. Or worse, from their viewpoint: becoming a movement that threatens the entire system and the status quo.
