The United States Senate is a defective, dysfunctional institution. It has been rendered virtually ineffective not so much by its original design (though that, too, is problematic), but by the adoption in 1975 of a rule that essentially requires 60 votes to get anything done.
The rule requiring 60 votes to invoke cloture on a filibuster means that it takes a super-majority to prevail in the Senate. As partisanship has grown more bitter on Capitol Hill, this has rule has become deeply problematic. The New York Times this morning quoted Senator Sheldon Whitehouse (D-RI), who, speaking on the Senate floor yesterday about the persistent obstructionism of Senate Republicans, said: "We have now crossed the mark of over 100 filibusters and acts of procedural obstruction in less than one year. Never since the founding of the Republic, not even in the bitter sentiments preceding Civil War, was such a thing ever seen in this body."
Writing about the "distorting and destructive effect" of this internal rule, Jim Fallows says that this situation "needs to be elevated from a background/insider's issue to absolutely first-tier consideration in mainstream political discourse." (See a follow-up on this issue by Fallows here.) I agree. Even without this debilitating and paralyzing rule, the Senate is the most flawed element in our government's constitutional design, giving far too much power to Senators from sparsely populated states. But the distorting effect of the 60-vote cloture rule makes the minoritarian tendencies of the U.S. all the more troublesome.
UPDATE: I see that in his column in this morning's Times, Paul Krugman weighs in on the same issue.