In theory the Senate passes legislation with a simple majority: 51 votes. But if a senator threatens to filibuster a bill by talking about it forever, then those who want it to pass need what's called a "cloture vote"-essentially a vote to end debate. But the thing is, cloture requires 60 votes. Recently we've needed more and more cloture votes (see the chart) because we've had more and more filibuster threats. Basically, lawmakers are getting less cooperative and it's really starting to prevent government from getting anything done.Chart via Ezra Klein.