Actual Senate supermajority requirements: 72 Democrats, 54 Republicans
A look at Senate voting habits shows that it takes only 54 Republican Senators to reach 60 votes for conservative legislation, while it takes 72 Democratic Senators to reach 60 votes for progressive legislation. While the last sentence sounds like snark, it isn't). Democratic Senators vote with Republicans significantly more often than Republican Senators vote with Democrats, making it much easier for Republicans to pass the kind of legislation they want.
According to Progressive Punch, looking only at "crucial votes," the average Democratic Senator has voted with the progressive position 82.4% of the time over the course of their entire career. By contrast, looking only at crucial votes, the average Republican Senator has voted with the progressive position 3.5% of the time throughout their entire career.
Voting habits like these mean that, in order to reach 60 progressive votes on crucial votes, Democrats actually need 72 Senators ((72 * 0.824) + (28 * 0.035) = 60.3 effective votes). By contrast, Republicans only need 54 Senators to break progressive filibusters of their agenda ((46 * 0.176) + (54 * 0.965) = 60.2...
