Republicans win when people think they can afford to vote R. Democrats win when people are sick of the Republican president.
All the politalk like this is some sort of complex conflict has been a big waste of everyone's time. The Trump administration will have to lose support for the Democrats to win, and the only way for any of that to happen is for them to carry on. Dems can keep looking under every cushion, they'll find nothing. The most important thing for them right now is to stop fighting and just tail Trump and the GOP on the impacts of everything they do on people. They have to stop thinking about strategies, candidates, districts, and so on, it's all just fuel for poliwonk bloggers who are just glad to have a job and suffer from tunnel vision and it completely distracts everyone, putting the focus on illusory and overblown party divisions instead of on actual politics.
There is no secret kung-fu technique or Buddha reincarnation to find, no revolution to start, none of that.
Democrats just need to speak directly to people about how they are negatively impacted by anything the GOP is doing or has done. It's boring, it's hard strenuous work, but that's how it is and how it has always been.