The filibuster operates like a veto today because Senate majorities are unwilling to use the rules to pass legislation. Senators may temporarily delay particular aspects of that agenda by speaking on the floor. But they cannot prevent the Senate from voting in perpetuity, because filibustering imposes physical and opportunity costs and because of the procedural limitations contained in the Senate’s existing rules and practices.
For example, Rule XIX limits how many times a senator may speak on the floor in a debate and it stipulates that when a senator is no longer able to talk, he or she has no choice but to yield the floor. At that point, the Senate votes on the underlying question unless another senator seeks recognition and then speaks for as long as he or she desires and is able. While the length of the Senate’s business delay is proportional to the number of senators who participate in a filibuster, there is no point at which business gets delayed indefinitely, since individual senators can speak for only a finite period. When no senator seeks recognition in a debate, the Senate must vote.
The Senate will rarely need to go to such lengths to overcome filibusters because simply debating a bill before trying to pass it creates buy-in among senators and builds bipartisan support for it.