West Virginia voted 70% for Trump. Manchin not doing what Biden asks would make his constituents happy. Also, Manchin isn't doing this out of political convenience. He appears to genuinely not agree, in principle, with overriding the parliamentarian or on a flat $15 minimum wage. So even if he would pay some consequence with the voters, he probably still wouldn't do it. And to top it all off, Manchin probably is not planning on running again so he doesn't even need to stay in the good graces of his conservative constituents. And when he leaves, he will almost certainly get replaced by a Republican since we only have a Democrat in that seat because he is popular with the people of that state. Otherwise, they are super Republican. So Dems are about to lose 1 more senate seat to a far right person, probably.