I don't see how democrats will be able to come up with a coherent platform, because right now, cost of living is probably the number one issue for American voters.
So how can democrats reduce our cost of living? They can't. Everything they support either restricts supply or makes production more expensive. The states with the highest cost of living are (of course) the most progressive, e.g. California, MA, NY, etc.
But wait, it gets worse. These states also have sky-high state and local taxes. This is what the left does: they make everything expensive, and then on top of that, they tax the living shit out of you.
Zohran Mamdani is going to win because his platform is focused on lowering the cost of living in NYC. However his "solution" is to subsidize demand in addition to even more government control over the economy. This has never worked, and will never work.
Lower prices come from capitalism and competition in (largely) free markets, and the left hates all three.