Speaker of the House Paul Ryan speaks to reporters after passing the Republican tax reform bill.J. Scott Applewhite / AP

With a little less than two weeks left in 2017, most Americans are winding down at the office and looking toward the holiday. Yet, Congress is just starting to get to work.

By its self-imposed deadline of December 22 (a deadline set after two delays), Congress still needs to: fund the government to prevent a shutdown, reauthorize the Children’s Health Insurance Program (CHIP), which expired more than two months ago, find a substitute for the Deferred Action for Childhood Arrivals (DACA) program, and provide disaster aid for victims of this year’s wildfires and hurricanes, as well as funding to combat the opioid epidemic—to name just a few.

It would be natural to blame this last-minute rush on the chaos of the Trump presidency. There is no modern White House that has been as slow to staff the government, has cycled through as many senior presidential aides so quickly, or had to contend with a far-reaching investigation and indictments of two of the president’s most senior campaign aides all in its first year. Not to mention the unique set of challenges the administration has had to face as a result of the president’s Twitter habits.

But the reliance on last-minute legislating is nothing new. In fact, it has been the norm for presidents, starting with Bill Clinton in 1993 and intensifying with each of his successors. Ironically, policymaking in the United States is broken because its politics is not. For the first time in a century, the two parties have been relatively balanced, ideologically coherent, and deeply polarized from each other. This has produced a politics that is more competitive than any other in the postwar era. Come Election Day, anything can happen, and with a good chance of being dealt a better hand the next time the polls open, there’s no reason to cooperate. As a result, nothing gets done in Washington unless it absolutely, positively has to.

From the end of World War II to roughly the end of the Cold War, American politics and policymaking was markedly different. The Democratic and Republican parties were internally diverse, with distinct factions that often did not agree with each other on fundamental issues. Liberal Northern Democrats, such as Senators Ted Kennedy and Walter Mondale, had to contend with conservative Southern Democrats. In the Republican Party, conservative “Regular Republicans” had to contend with liberal Northeastern Republicans, like New York’s Jacob Javits and Massachusetts’s Edward Brooke (the “Rockefeller wing”). To pass anything, parties had to reach across the aisle to find willing partners from the other party—partners that changed depending on the issue.

On civil rights, for instance, to pass the landmark Civil Rights Act of 1964, Democratic President Lyndon Johnson relied on the votes of 25 Republican senators, including all 16 Northeastern Republicans, to end a filibuster by his fellow Southern Democrats. On economic policy, Republican President Ronald Reagan in 1981 relied on the votes of 50 “boll-weevil” conservative Southern Democrats to pass his budget—and later tax cuts—through a Democratic House of Representatives.

To many, this cross-party dealmaking was a sign that American politics was broken. The American Political Science Association called for “responsible” political parties who could present a coherent platform, ostensibly be elected on it, and then implement its planks. Others lamented the seemingly intractable divided government—in which Republicans reliably controlled the presidency and the Democrats controlled the Congress—of the 1970s and 1980s, going so far as to call for four-year House terms so that members of Congress were tied to the presidential ticket.  

Beginning in the early 1990s, however, the political parties started to become more ideologically coherent and competitive, and the result was the broken policymaking we see today.

By the end of the century, conservative Southern Democrats and liberal Northeastern Republicans had become extinct. By 2001, not a single Republican member of the House was more liberal than any Democrat, nor a single Democratic member of the House more conservative than any Republican. As the University of Wisconsin-Madison political scientist Byron Shafer noted, by the Obama era, the number of House Republicans who were either closer to the ideological midpoint of the Democrats or to the ideological midpoint of Congress overall was essentially zero; for the Democrats, it was sub-10 percent. Both of these numbers were down from over half in the late 1950s.

Not only were the two parties more polarized than at any point since the late 19th century, they were also more balanced.

Consider that since 1992, the United States has had every single possible permutation of Democrats and Republicans controlling the House, Senate, and presidency. Contrast that with the stability of the years 1968 to 1992 in which Congress was controlled by the Democrats, and the presidency was—with one post-Watergate exception—controlled by the Republicans.

With two ideologically coherent, evenly matched parties facing off, politics is more competitive, but it leads to broken policymaking. Since each election could mean a reshuffling of power in Washington, the best strategy is to stall the other side, not work with them. From this logic, it made perfect political sense for then-Republican Representative John Boehner to state in 2010 that when it came to the Obama agenda, “We’re going to do everything—and I mean everything we can do—to kill it, stop it, slow it down, whatever we can.” And it makes perfect political sense for Democrats to uniformly oppose the Trump agenda.

That is why absent a true crisis—such as was the case in the wake of the terrorist attacks of September 11 or the financial collapse of 2008—or unless members of Congress have no choice, such as when the government is on the verge of defaulting on its debt or shutting down, will they act. And when they do, it’s not the careful debate of individual policies, but rather “omnibus legislation”—a giant log-roll that pulls all these pent-up policy demands into one legislative spasm that includes enough to make both sides happy.

It’s what we saw throughout the Obama presidency, it’s what we will see in the Trump presidency, and it’s why Congress is spending this holiday season hard at work, legislating.

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