The modern fillibuster is a general agreement to let other Senate business happen while a particular vote is postponed. But Republicans want to enforce some of the older rules that mean that when a filibuster is happening, no other business can take place.

Thune is smart to proceed cautiously. There are a lot of other things that Republicans want to get through the Senate, including the DHS funding bill, and the Senate’s HR role of approving appointments. Given the state of the current rules, Democrats can hold up the voting bill without stalling all that other stuff. Once they pull the trigger on this, that all changes. Schumer will start reading names out of the Park Slope phone book for weeks on end, and all that other stuff doesn’t get done.