historically there is always the one or two who (perhaps too conveniently?) block or water down legislation: joe lieberman against public option [0], two democrats block student debt relief [1], the dynamic duo of manchin and sinema blocking voting rights legislation and build back better [2] [3]...
you don't need to blame republicans for democrats sabotaging themselves over and over.
[0] https://www.motherjones.com/politics/2009/12/joe-liebermans-...
[1] https://www.businessinsider.com/which-democrats-voted-to-blo...
[2] https://apnews.com/article/biden-voting-rights-bill-collapse...
[3] https://www.nbcnews.com/politics/congress/manchin-says-he-no...