Best bet is to try and support politicians based on the money they take during their campaign. It's the only real way to distinguish Democrats masquerading as "left leaning" with nice soeeches and rhetoric and ones who actually are.
I always plug opensecrets.org for that since it makes it pretty easy to just go to the campaign finance section, search a politician and see exactly where the majority of their funding comes from. Those are the groups they're going to try and please. It's why people like Sanders and AOC are free to actually speak the truth for the most oart, they're only behokden to the normal people who fund their campaigns with small donations.
Opensecrets also gives a lot of good information that breaks down how to effectively research campaign finance.