The GOP's debt ceiling cynicism is just the beginning.

In 2006, Democrats won a landslide victory at the polls, sweeping to majorities in both houses of Congress. And then, the Democrats proceeded to do … hardly anything at all. Their agenda consisted mainly of halting George W. Bush’s domestic agenda. Even on the Iraq war, the unpopularity of which fueled the Democratic wave, the party did not make a serious effort to defund the campaign. Ultimately, Democrats funded a troop surge.

The rough equivalent would be if Republicans this year wound up expanding the Affordable Care Act to cover illegal immigrants. (To make the parallel between 2007 and the present more exact, we’d have to imagine that Republicans control the entire Congress, not just half, and that President Obama has lost about a quarter of his current popularity.) This scenario, of course, is unimaginable. 

What are we to make of the contrast? One conclusion is that the GOP is the more disciplined, parliamentary party. I’ve made this case myself. But that is not the only implication, or the most disturbing. Why didn’t the Democratic Congress behave under Bush like the Republican-controlled House has behaved under Obama? Why didn’t it simply refuse to fund the Iraq war or to threaten financial cataclysm by holding the debt ceiling hostage unless Bush, say, raised taxes for the rich?

It is hard to formulate an answer other than: Nobody ever considered the possibility of using the power of Congress this way. Now that Republicans have demonstrated the vast power available to an opposition party willing to deploy it, the sort of crises that have gripped Washington this summer will probably become a regular feature of American politics. What’s been exposed is not merely the weakness of the U.S. economy or the paralysis of its fiscal policy, but the instability of its very political system.

The American political system, as you probably learned in high school, was not designed to accommodate political parties, but it produced them almost instantly. The first eight decades saw a series of crises, from the Alien & Sedition Acts to the Nullification Crisis to the Civil War. After the Civil War, politics calmed down, and white Northerners and Southerners settled a peace based on the persistence of racial apartheid in the South. This led to nearly a century of oddly heterogeneous parties.

In recent decades, the two parties have sorted themselves along ideological lines. An endless stream of establishmentarians has decried the rise of “partisanship.” What is actually going on is a confusion about political legitimacy that’s inherent in our system. Political scientist Juan Linz once observed that parliamentary democracies have a superior record of stability to presidential democracies. In a presidential system, he noted, the question may always arise, “Who has the stronger claim to speak on behalf of the people: the president or the legislative majority that opposes his policies?” To this dilemma the presidential system offers no solution save raw assertion of power.

Historically, we have avoided these contradictions through social norms that could sustain themselves in a government with weak parties. Congress confirmed the president’s appointments except in extreme circumstances because, hey, that’s the way we do it around here. But what if the opposition decides to do things differently? Jimmy Carter and Ronald Reagan had more than 90 percent of their judicial nominees confirmed. The next three presidents had 79 percent, 84 percent, and 87 percent. Obama? Just 61 percent.

Republicans in Congress have begun blocking even presidential appointees to the executive branch, sometimes for ideological reasons, sometimes to protest unrelated actions, and sometimes just to gum up the works. Republicans in this Congress have announced they will block any appointee to agencies like the Consumer Financial Protection Bureau and the Independent Payment Advisory Board unless Obama agrees to rewrite the laws governing them. Brookings scholar Thomas E. Mann told my colleague Jonathan Cohn that this unprecedented refusal to allow the functioning of a duly passed law harkens back to nullification. But the fact that this sort of obstruction is unprecedented does not make it wrong. It merely violates custom.

The debt ceiling showdown offers a classic episode of competing claims to legitimacy. The Republicans’ position is that, having won the House in 2010, they now represent the popular will. On that basis, they could use the dire threat of failing to raise the debt ceiling to compel Obama to adopt their policies wholesale. “The principle of not raising taxes is something that we campaigned on last November,” announced John McCain this year, “and the results of the election was that the American people don’t want their taxes raised and they wanted us to cut spending.” Surely McCain of all people could think of another recent election conferring popular legitimacy on a branch of government for four years. But no, he believed the results of the 2008 presidential election had been superseded by the midterms.

As the parties have drifted further apart ideologically, they have searched ever more diligently for weapons in the war of legitimacy. The debt ceiling is merely the latest—once just an opportunity to posture against the incumbent’s fiscal record, it is now being used by Republicans as a hostage to force policy concessions.

It is not as though the presidency has fallen into helplessness. Quite the opposite: In those fields where it can avoid congressional affirmation, the executive branch has grown more powerful. The ratcheting up of executive authority over intelligence and foreign policy is well known. Obama, no less than Bush, has found new powers of office to evade congressional inaction. The Treasury Department ran tarp. The Department of Education threatens to use federal waivers in lieu of Congress updating No Child Left Behind. Rather than overturn the Defense of Marriage Act, Obama refused to defend it in court (a practice liberals might not like if applied to some other law). Other examples abound. These are not countervailing powers so much as escalatory powers.

We can only imagine what other devices lie in store, never previously deployed only due to a social convention nobody thought to disregard. Consider: Senators previously felt obliged to confirm all but the most radical Supreme Court nominees. Now that they can mount a filibuster, why should Republicans confirm even a moderate liberal? Why not demand a conservative? The frightening thing is that this age of discovery of unused weapons is young.

Jonathan Chait is a senior editor at The New Republic. This article originally ran in the August 18, 2011, issue of the magazine.