Unlike the US House of Representatives which enforces time limits on all debates, the US Senate has no time limit on debates. So this gives senators in the minority an opportunity to forestall a vote by extending debate (or filibustering) as long as they choose to. At one time, senators had to actually talk continuously to maintain the filibuster but Senate rules now even make that unnecessary. At present, a motion of cloture or ending debate requires the vote of 60 senators.
If nothing else, the filibuster is now being used far more often than it used to be when it was reserved for especially controversial legislation. The idea of extending debate on especially important or controversial legislation has its appeal especially if it leads to some thoughtful discussion that may influence some votes in the process. But when it is used in a routine manner to do nothing more than block legislation based on strict party lines, the minority has a means to paralyze the whole Senate process indefinitely which makes it so controversial.
Not surprisingly, conservative commentators like Ross Douthat in his NYT article The Filibuster, Now More Than Ever? supports another writer who thinks the filibuster as now being employed by the Senate Republicans is a swell idea.
In the absence of a filibuster, a polarized political system would produce wild policymaking swings, with Al Franken writing legislation one session and Jim DeMint writing it the next. Its presence requires even the most ideologically-charged majority to cut some deals before it rams legislation through.
The current 60-vote requirement to cut off debate empowers a tiny minority of Senators to prevent up or down votes on measures that clearly have majority support in the Senate, and overwhelming support among the American people. It is a fundamentally undemocratic procedure that is now used regularly by the most entrenched economic interests in America to prevent change.
It has been pointed out that the filibuster is a Senate rule and is not in the Constitution which as written allows laws to be passed by a simple majority in each house of Congress (with exceptions such as Constitutional amendments). It is a bit curious that conservatives who so often base their arguments on preserving what they feel is the original intent of the Constitution seemingly have no problem with a Senate procedure that turns this original intent of the Founding Fathers on its head.
While Creamer outlines a number of arguments in his blog for changing the Senate rules on filibusters, the Republicans may want to reconsider their recent overuse of the filibuster for their own self-serving reasons. While the presidency and Congress are now controlled by Democrats, the Republicans naturally would like to have one of their own someday elected to the White House along with regaining majorities in Congress to enact some of the laws that they favor.