If a foreign adversary wished to break American politics, it might go about it like this: Step 1: Support extremism on both sides of the political spectrum. Step 2: Make American politics feel higher-stakes, even more divisive. Step 3: Support candidates who reduce politics to winning and losing, and make everything feel zero-sum. 

Because America has a divided two-party system, such a strategy would make American politics more polarized and leave less middle ground. And because the American system of government is set up to require a good amount of compromise, such a strategy would make American democracy less responsive and more gridlocked.  Frustration and resentment and anger would spill over, poisoning the polity. Eventually, the already brittle American political system would crack. 

This is exactly what Russia has been doing to American politics for years. Russians have found the weak spot of American politics, the zero-sum scorched-earth partisanship destroying our political institutions, and they are exploiting it. 

But why now? The American system of government has been around for more than two hundred years. Our 1787 Constitution was a compromise between states of varying size and economic foundations, some of whom feared domination by others. So the theory guiding the complex design of American institutions was something like this: It should be hard for narrow majorities to form, because narrow majorities could oppress minorities. 

The Founders had read their history. They knew how it easy it was for political systems to fall into civil war when the polity split into two opposing parties (see: Greece, Rome). They thought that by spreading power around (a bicameral legislature, a separately elected president, plenty of powers reserved for the states), they would prevent majority parties from forming. Policymaking would proceed slowly and carefully—through deliberation and compromise—to ensure that no laws were enacted without wide-spread support.

Despite their best intentions, political parties formed almost immediately, and because elections were held using a winner-take-all, first-past-the-post system, just two parties emerged.

At the heart of the early American political system, there was an underlying tension between North and South over two very different visions of labor, one free, one slave. However, for the first part of the 19th century, the two great political parties had both Southern and Northern wings. As a result, the low-simmer political battles over slavery existed between the two parties. This kept the national peace, but it prevented any resolution of the slavery question. Both parties had an incentive to avoid the issue, since it would divide them internally. And so tension grew beneath the surface of national electoral politics.

In the 1850s, as the country expanded westward, the slavery question demanded a resolution. Both major parties, the Whigs and the Democrats, split apart over it. The new Republican Party combined the northern Whigs, some anti-slavery northern Democrats and a few other splinter parties into a winning plurality. In a four-candidate 1860 election, Abraham Lincoln won with just under 40 percent of the popular vote. Southern states feared a country run by northern Republicans would oppress their “way of life.” As American politics fell into a binary in the 1850s, both sides radicalized. Once the space for a compromise middle ground vanished, a rebellion became a four year civil war. 

Perhaps slavery could have been resolved through gradual, compensated emancipation (or another, more progressive compromise solution), perhaps it couldn’t have been. But it turned to civil war at a very precise moment. It became a civil war when the American party system divided in half on the polarizing issue, and the half of the country slightly in the minority feared that the other half of the country, which had the majority, would use its power to enact radical change. In short, the Civil War revealed the fragility of the American political system when political conflict turns to a binary, zero-sum conflict over national identity, and its tendency to radicalize both sides into escalating conflict. 

Analysts frequently claim that American society is more divided today than at any time since the Civil War. They cite various measures of partisan polarization, which have been increasing steadily for decades.1 Once again, the nation is split over fundamental questions of national identity. 

One party based in urban, cosmopolitan America, sees diversity and progressive cultural values as central to American identity. They see the promise of America as yet unfulfilled, a work in progress, overcoming a troubled past towards a more just and fair society. 

The other party, based in rural, traditionalist America, sees America moving in the opposite direction, a declining society that has lost its greatness by moving away from its traditions—traditions in which white, Christian, men were atop the social hierarchy. 

And once again, our political system does not offer an easy resolution. Framed as a binary conflict between progress or revanchism, or between decline and restoration (depending on partisanship, of course), there can be no easy compromise. Certainly, many Americans themselves might see the alternatives in less stark terms than their political leaders. But in a binary, two-party political system, with both parties defined by their most active and extreme enthusiasts, participating in politics means picking a side. And in a lesser-of-two-evils two-party system, political leaders try to draw stark contrasts in order to define the other party as out of bounds, disqualified, and ultimately, un-American. 

One way to think of our political system is like a creaky old thermostat with just two settings: hot and cold. Imagine a large family living in a household with such a thermostat, fighting over the temperature. Half the family likes it a little cool, half the family likes it a little hot. But since the thermostat has no middle setting, when those who prefer it cool take control, they adjust the cool setting to be even cooler to over-compensate for the hot room. The same happens when those who prefer it warm take control; they make the hot setting even hotter. 

Now imagine the creaky old thermostat resisting change and being slow to respond, so the more aggressively the family fights over control of the thermostat, the worse the thermostat functions. They have to set it even cooler or hotter to have a chance at getting their desired temperature. Eventually, an all-out fight will break out in the family, and/or the HVAC system will break under the strain. 

This is not a resilient system. Once it starts, an escalating fight for control of the thermostat, it has a tendency to escalate further. It is a reinforcing feedback loop, a “doom loop,” with no release. 

You can imagine a better designed thermostat: It should have more settings, making it easier to collectively agree on a mid-point. This would prevent one side from grabbing control from the other and allow for compromise, i.e. a temperature everyone can live with.

And indeed, most advanced democracies have developed a better, more resilient political system that avoids this binary escalation. Most advanced democracies have proportional, multiparty representation. That is, rather than selecting representatives through single-winner plurality elections, they select representatives through multi-winner, proportional elections. A larger constituency winds up represented by several political parties, in direct proportion to their support within the district. Parties then form coalition governments after the election.

At a first glance, this kind of electoral system can look chaotic and fractious. It makes it easier for extreme, fringe parties to gain representation. And sometimes it takes months to form a government after the election, as parties engage in elaborate and difficult negotiations. But as with all complex systems, some short-term instability is necessary for long-term stability. It allows the system to make more gradual, iterative adjustments to external pressures. And some representation for extremist fringe parties can be better than no representation, because it brings their concerns into the open and lets their supporters express their frustration, and forces the system to respond. In the American two-party system, fringe extremist sentiment has instead taken over one of the two major parties, where it is much harder to isolate because its ideas are now intermixing with long-standing partisan loyalties.

While the same global pressures are affecting politics in both the United States and Europe, European multi-party systems have responded somewhat differently. The old Social Democratic parties, built in an earlier era, are ceding ground to new Green parties, which many believe are better fitted for the current era and its climate challenges. And as old center-right parties, also from an earlier era, have struggled, new center parties have emerged to fill the space. In a more competitive marketplace of political partisanship, new parties can emerge and gain supporters more easily to give voice to emergent constituencies, and fill unoccupied political space. This short-term flexibility allows multiparty systems to be more resilient, and responsive to changing global dynamics.

By contrast, in the American two-party system, the Democratic and Republican Party continue to lumber along as they drift towards extremism. They are incapable of extinction because the plurality-winner system of elections renders third parties spoilers and thus highly improbable. Democrats form the natural opposition to Republicans, Republicans serve as the natural opposition to Democrats. So it has been, for 160 years. 

But what’s different today is that American politics is now so fully nationalized. In the past, when local politics weighed more heavily, the national party system had more flexibility. The Democratic Party mixed southern conservatives and northern liberals. The Republican Party mixed western conservatives and eastern liberals. American politics operated more like a four-party system, which fluid coalitions. But as politics nationalized, that loose-jointed flexibility dissipated. The two parties became more distinct, sorted, and less responsive. Their division ran up against an American political system designed to force compromise and super-majority support for new legislation.

The only way to make the American political system more resilient is to bring back that flexibility—to add more settings on the thermostat of American politics, and give space for new ways of setting the temperature. The best way to do that is to change how we elect members of Congress. Get rid of our ancient first-past-the-post plurality system of elections, and join most advanced democracies by using proportional representation. Many varieties of proportional representation exist. Some, like Israel’s, make it too easy for small parties to form and generate overly fractious politics and overly complex coalition building. The number of parties depends on various political engineering choices relating to ease of small party entry. Between four and six parties is ideal—enough to give voters meaningful choices and enough to expand the fluid possibilities for coalitions, but not so many that the system fragments into too many pieces.

The best way to do this would be to adopt a system that the Irish have used successfully for almost 100 years: multi-winner House elections in five-member districts, with ranked-choice voting. This would ensure some proportionality (Ireland has typically had between three and five serious parties). The Senate is more difficult to make proportional, but ranked-choice voting in Senate elections would make space for new parties and replace the zero-sum nature of the current political binary.

Our zero-sum partisan binary is brittle. For now, it is stuck, because it’s hard to shift an old political system designed to resist change. But at some point, that frustration will lead to destabilizing radicalism and the smashing of an unresponsive system. Accepting this as inevitable makes the choice simple: Add more flexibility and resilience now, or let us remain vulnerable to foreign adversaries who have found the weakness of American democracy and are exploiting it daily.

Could change really happen? Enough Americans are frustrated with the status quo, and few elected officials enjoy the zero-sum partisan warfare. A new set of electoral rules that has no obvious partisan tilt because it challenges both parties could offer a genuine truce. Most likely, reform will begin in the states. Already, Maine has passed ranked-choice voting, an electoral reform that makes it easier for more parties to compete by removing the spoiler effect of third parties. The reform is gaining momentum. It looks more and more like the first step in a new era of political reform, innovation, and renewal.