Why Is America Always Divided 50–50?

Despite wrenching economic and political changes in the country, Democrats and Republicans keep finding themselves nearly tied in election after election.

Illustration of a hand holding a coin
Katie Martin / The Atlantic; Getty

Republicans and Democrats once again find themselves in a dead heat as they fight for control of the American government. The Senate majority hinges on a handful of seats. Republicans are likely to retake the House, but unlikely to eke out a strong majority. The generic ballot shows that 46 percent of Americans prefer the GOP and 45 percent the Democrats.

The two parties have been neck and neck since long before this midterm. Despite wild gyrations in the economy, the terrifying rise of antidemocratic politics on the right, and yawning policy differences between Democrats and Republicans, recent national electoral results keep coming in remarkably close, as if decided by a coin toss. A few decades ago, a Democratic president being 15 points underwater on his approval rating likely would have led to a Republican wave in the midterms. This year, political analysts expect more of a ripple.

Many statistics point to the same trend. The frequency with which the House and Senate flip between parties has increased; neither party builds much momentum for long. Democrats controlled the House from 1955 to 1995, for instance. Now the chamber is about to change hands for the fourth time in 15 years. The difference in the number of congressional seats held by the majority and minority parties has collapsed too. Between 1959 and 1995, the House majority was never less than 50 seats and repeatedly hit the triple digits. Today, the Democrats have only eight more seats than the Republicans. The popular-vote margin in American presidential elections has diminished too. In five of the past six contests, fewer than five percentage points separated the winner from the loser.

Every election is close. Every election feels consequential, because it is. And far-reaching policy outcomes are over and over again determined by just a few thousand votes in a handful of states.

In many ways, this is a baleful trend. Our coin-toss elections are not the result of having two parties competing for an engaged and persuadable electorate. They are at least in part a product of our political stasis and extreme polarization. They mean that when either party wins, it does so without much of a mandate. They also mean that neither party is ever forced to regroup and reform after a humiliating defeat. In the words of the Princeton political scientist Frances Lee, both parties are “insecure” in victory and hyper-engaged in a “perpetual campaign” against the other side.

There is no simple explanation for why this is happening. I had at first figured it had something to do with game theory. You have two parties. Each has deep resources and strong incentives to win over and thus reduce the number of middle-of-the road voters. The parties zig, they zag, they revise their arguments. They both get better at winning elections, beefing up their use of voter data, opposition research, on-the-ground organizing, and gerrymandering. In time, each gets good enough that the contests start to come out 50–50.

That hypothesis might be partly true, John Sides, a political scientist at Vanderbilt University, told me. But he pointed to historical factors that, in his view, offer the strongest explanation for today’s political environment. During the Great Depression, the Democrats became a nearly unshakable majority party in Congress, buttressed by the votes of white southerners and New Deal supporters across the country. But in the 1960s, white southerners began migrating to the Republican side in a revolt against national Democrats, who backed civil-rights legislation and redistributive policies that aided Black Americans. As the political saliency of the New Deal faded, the parties became more competitive and their voter bases more equal. “The thing that made us so unusual for so long was the South,” Sides said. “We had a one-party state within the country.” Its disappearance paved the way for our 50–50 electorate and pendulum-swinging government.

Indeed, as Lee describes in her excellent book Insecure Majorities, the Republicans became a “full-fledged, politically viable national alternative to the Democrats” only in 1980, when Ronald Reagan won the presidency on a low-tax, small-government platform. The same year, Republicans took the Senate for the first time in a quarter century. And in 1994, they broke the Democratic grip on the House.

A related explanation for today’s instability has to do with the growing polarization of the two parties. In the early half of the 20th century, Democrats and Republicans had considerable policy overlap, and legislators worked across the aisle frequently. Since then, their policy differences have become sharply pronounced. Voters changed too: They quit splitting their tickets and became more reliable supporters of one side or the other. They “sorted” along political lines, becoming more likely to live around people who vote like them, as well as becoming more ardent ideologically, with fewer cross-cutting social ties, a phenomenon described by the political scientist Lilliana Mason. They also became more averse to partisans of the other side. That polarization has contributed to our close elections: When almost all voters have already made up their mind, there just aren’t that many people for politicians to persuade.

As Lee shows in Insecure Majorities, such close contests and frequent changeovers in power are a cause of partisan strife. In recent decades, “neither party perceives itself as a permanent majority or permanent minority,” she writes. “This shift altered members’ partisan incentives and strategic choices in ways that help drive the sharp and contentious partisanship that is characteristic of contemporary American politics.” These days, both Republican and Democratic leaders have less incentive to cooperate across the aisle. Why give the other side a legislative victory if you are so close to taking back the House or winning the Senate?

The competitiveness of American elections also seems to have made the government less responsive to the wants and needs of voters—not more so, as you might normally expect. “In the current context, you have party control that hinges on small margins of the vote share in a small number of races,” Sides said. “A narrow shift creates a vast difference in terms of how the country is governed. Is that really what the election mandate was? Is that what voters want? I’m not so sure.”

Never losing by a significant margin or for a long period of time seems to have been bad for the parties themselves as well. Being banished to electoral purgatory every now and then encourages political groups to reform and change. It encourages them to think about their long-term value proposition, not just how to gain a few thousand more votes in Wisconsin. It forces them to adapt to the needs of average voters. Our political climate has diminished that constructive pressure for both sides. (Consider how many times Republicans have ignored their own advice about moderating and being friendlier to voters of color, opting instead to run some version of the “southern strategy” over and over.)

Yet for both sides, being out of power for any considerable amount of time feels like an existential threat. And for both sides, holding power for any considerable amount of time feels like an impossibility. Whatever happens this election, the next is likely to undo some of it—giving voters a greater sense of insecurity and urgency, with so much on the line each and every time.