I want to plug to an excellent Note that was just published in the Yale Law Journal. Benjamin Eidelson does a thorough analysis of Senate filibusters to assess how many of them actually represented states with a majority of voters. The answer is that it’s not uncommon. Imagine that 41 Senate Democrats filibuster something, and that group includes the senators from New York, California, and Illinois. You can see how it is possible that a Senate minority could represent a voting majority.
When I wrote my article on cloture reform two years ago, I acknowledged this possibility but noted that there was no reliable data on that question. Now there is.