I've written several articles on progressive politics and on the core (politically incorrect) difference between progressive and conservative characters. I think you're understating the problem for progressive politicians. Mind you, any explanation of the weakness of liberal or progressive politics must account for the success of FDR and Johnson, including the New Deal and the Great Society.

https://medium.com/@benjamincain8/femininity-and-masculinity-in-american-politics-24e774288043?source=friends_link&sk=21e247efcbc74bbd7f2d8250fe644eaf

https://medium.com/discourse/why-democrats-are-inept-at-politics-b0bbe6648fb9?sk=155f6641cd7ddc511c52328ec4ce76f7

https://medium.com/discourse/the-hidden-depths-of-the-democrats-ineptitude-9a8ba883c806?sk=702a3d92f37c43ac73cb050ecb0de12e

https://medium.com/discourse/how-democrats-bring-a-knife-to-a-gun-fight-415c04884deb?sk=560acb7306c3e05c5c435c82e55ca4f7

https://medium.com/discourse/why-democrats-are-as-nihilistic-as-transactional-trump-fa3a0f57573e?sk=483d890061a23663c01fa29c104f676e