http://www.slate.com/articles/news_and_politics/politics/2010/02/let_the_majority_rule.html
Key Takeaway:
What do these calculations reveal? First, over the past two decades or so, the senators who successfully filibustered something represented about 46 percent of Americans on average. Yes, that is a minoritybut it is a far cry from the nightmare scenarios sometimes deployed by opponents of the filibuster, who worry that as little as 11 percent or 12 percent of the country could obstruct popular legislation. Since 1991, in fact, there have been only four filibusters3 percent of the totalthat thwarted senators representing more than 65 percent of the American people.*
What's most striking, though, are the many cases in which the filibustering Senate minority has actually represented a majority of Americans. In fact, in 40 percent of the filibusters since 1991, the senators making up the "obstructionist" minority represented more people than the majority they defeated.
This example is typical of a more general partisan pattern.
When Republicans have been in the majority, the filibustering minority has actually represented the majority of Americans 64 percent of the time. When Democrats have been in the majority, that figure plummets to 3 percent.