I've always been a little ambivalent about the "broken branch" thesis. On the one hand, Thomas Mann and Norman Ornstein make a good case that things have gone downhill in both houses of Congress since the glory days of Lyndon Johnson and Sam Rayburn. George Packer has made the same argument, specifically about the Senate,in The New Yorker.
Actually, no one has issued this indictment more eloquently than Senator Glenn. Looking back on his long career, he writes:
In my twenty-two years in the Senate, I had watched the legislative process change. There was always partisanship--that was the nature of the system. Although it produced disagreement and debate, it ultimately forged budgets and laws on which reasonable people could differ but that worked for most. In general, lawmakers performed their duties in an atmosphere of mutual respect.
This was no longer the case. By the 1994 election, we had single-issue candidates, the demonization of government, the sneering dismissal of opposing points of view, a willingness to indulge the few at the expense of the many, and the smug rejection of the claims of entire segments of society to any portion of the government's resources. Respectful disagreement had vanished. Poisonous distrust, accusation, and attack had replaced it.
On the other hand, sometimes it seems to me that maybe the good old days weren't all they're cracked up to be--and, as a wag once suggested--never were! Certainly, the vicious caning of Senator Charles Sumner, of Massachusetts, by South Carolina's Preston Brooks in 1856 (pictured above) hardly qualifies as "respectful disagreement."
On the third hand, you can make the case that what's wrong with Congress is that its powers have been usurped by an all-consuming executive branch whose mandate comes from what James Madison referred to as "the superior force of an interested and overbearing majority." Or you could argue that Congress has simply abdicated while th executive--and the judiciary--have been flexing their muscles. Either way, the explanation for Congressional irresponsibility starts to sound like the old saw about academic politics: it's vicious precisely because "the stakes are so low."