I admit it seems unlikely, but they have done it before.
The largest faction within the Democratic Party is made up of political opportunists. The Dems spent 90 years as the party of Jim Crow, and then dropped racist principles like a hot rock, when they thought it was politically expedient. They were the party of progressivism for 40 years, then dropped progressive principles, when they began losing them elections.
The progressives within the Democratic Party believe the purpose of the Party is to push progressive principles. The larger faction within the Party has no principles, and will be quick to abandon progressivism, as soon as they think it is costing them votes.
Your assessment is right on the mark, in my view. The hard core progressives have, however, seized control of the purse strings and without money its going to be hard to flip and flop as they have done in the past. They may certainly stage some feint and say that they are abandoning their leftist leanings, but they will be lying.
The Democrats abandoned progressivism?