I don’t think Mamdani and such has been about moving the existing Democrats to the left. I think it’s about proving leftist policies elect people and so it opens the door for new people to replace centrists both running within the party and independents. Existing Democrat cadres would emulate that only as last resort. Leftist policies are both populat and they work in taking money from the owner class and distributing it to people who work for a living. If the owner class lets too much of it getting traction within one of their parties, they risk the policies sticking and people demanding implementation. Which means loss of profit and wealth, which woud diminish their power in society, which could trigger more wealth loss, and so on - in a feedback loop. This is why they can’t let their representatives flirt with leftist politics too much. Which is why I don’t think the Mamdanis and Polanskis of the world are going for moving existing parties left. Rather they’d be replacing (some of) them. Not saying a move to the left in existing parties can’t or won’t happen but it’d be difficult and it’d happen after they’ve lost enough to force it.