Why doesn't the Senate just require a majority to pass a bill?

#2 is technically correct–it is true in the context of a “real” filibuster, but wrong in the context of how the filibuster works in the senate today.

A true, Mr Smith goes to Washington filibuster stops all business in the senate.

That was understandably difficult–and so the “procedural” filibuster was born–the basic concept being a “procedural” filibuster simply precludes a vote–but does not stop debate on other topics. This makes it a very low-cost exercise–such that, as we see today, it is possible to “filibuster” more or less every bill, creating the 60% supermajority requirement.

For efficiency, here is my prior description of the process.

I’ve posted on filibusters before–here are two other posts (in useful threads).

http://boards.straightdope.com/sdmb/showpost.php?p=10518168&postcount=2
http://boards.straightdope.com/sdmb/showpost.php?p=11826931&postcount=4