evidence: How can a filibuster be beaten? The filibuster is not in the Constitution and is generally recognized as an accident of Senate rules. A bill is considered "filibuster-proof" if it has the support of at least 60 senators (it used to require 67 until a rule change in 1975). But few bills meet that criteria in today’s hyper-partisan political climate, especially with the Senate’s current 50-50 split between parties.