But with Sanders leading the pack, it’s no longer winning the top job, it’s down-ballot. If they kick Sanders off, they lose, since his voters will be gone with him. If they leave him on, they lose, because of the people you identify as not wanting to live in a Communist country (with my parents being two of them).
But down-ballot, my parents will still vote if Sanders is on the ticket, they just won’t vote for him. They’ll pull D’s the rest of the way. But if Sanders supporters are pissed because the Democrat Party screwed him out of the nomination, then they don’t vote down-ballot - maybe just stay home (since their anger will be at the party).
EXACTLY the same happened in 2016. Paul Ryan was set to steal the nomination from Trump at the Convention, in order to prevent a Hillary victory - but then down-ballot Republicans heard from us that they too would be punished if that happened, and Ryan pulled back, and allowed Trump to lose in a landslide (LOL), while protecting down-ballot candidates.
At some point fairly soon, the Democrats will realize that they have no way to beat Trump (barring some kind of black swan), and that, no matter what they do, their hold on the house will be in jeopardy. Your parents may still vote Democrat, but others won’t. Listen to the CSPAN callers after Pelosi tore up Trump’s speech. These voters are *done* with the Democrats. But a Sander’s campaign would be a daily tearing-of-the-speech. Some may stay Democrat. But some won’t. And that is the Democrat’s problem.
The bigger problem though is that the Democratic party is made up of rival fiefdoms. These fiefdoms are vicious and ruthless. Sanders (actually, his supporters), are interlopers. The Democratic power bases cannot tolerate a new, out-of-control, group to upset their delicate balance.
There is no parallel between the Republicans and Democrats here. The dynamics are just completely different. To survive, the Democrats need the Sanders voters to either shut up and do what they are told, or to go away permanently. The former is out of the question, so the Democrats have no choice but to force them out.
For the Democrats, this is no longer about winning the 2020 election. This is about surviving as a major party. They can do so, if they rid themselves of Sanders voters. But they simply cannot, if they don’t.