The latest Bloomberg Businessweek examines changes in congressional operations that have led to a growth in gridlock.

For much of the 20th century, committee chairmen were the most powerful people in Congress. They could hold up bills or bring them to a vote. In the 1970s political scientists looking at how Congress worked didn’t believe parties much mattered, because each member had a vote and a unique set of incentives. Party discipline was less important because it was impossible to enforce; interests within parties were too varied. Since the early 1980s, however, political parties have become more homogenous. Once you can get a whole party to agree on something, discipline becomes possible. Once it’s possible, it can be wielded as a weapon.

That started to happen in the late ’70s and early ’80s. Democratic Speaker Tip O’Neill forced the chairman of the House Committee on Rules to answer to the speaker’s office, a small change with far-reaching consequences. The speaker began writing the rules for debate on every piece of legislation. After the midterm elections of 1994, the new GOP speaker, Newt Gingrich, continued the work of asserting party control. Where committee chairs had been passed down by seniority, Gingrich appointed younger members loyal to him.

Dennis Hastert, the Republican speaker during most of George W. Bush’s presidency, took this demand for loyalty further. The Hastert Rule, an informal edict not codified in any book yet still followed, instructs the speaker not to bring any bill to the floor that doesn’t have the support of the majority of the majority. When Democrat Nancy Pelosi became speaker, she got rid of earmarks, giving up the power to bribe Republicans for their votes. John Boehner has largely upheld the principle that even a passable bill, if it can’t pass by a majority of his party, is not worthy of being brought to a vote. The recent stalemates are simply the logical result of a long-term trend: The party had become more important than the House’s business.

“You should be depressed,” says Keith Poole. “It’s going to get worse.” Poole, a political scientist at the University of Georgia, has spent three decades studying congressional votes that stretch back to 1879. With collaborators Howard Rosenthal of New York University and Princeton University’s Nolan McCarty, he’s found that members of Congress are now less likely to vote against their party than at any time since the first decade of the 20th century.

Of course, gridlock can create dysfunctional government, which is not necessarily a bad thing.