Two major political parties have long dominated politics in the United States. And since the mid-1800s, those two main parties have been the Democrats and Republicans. Why do American voters generally face fewer choices at the ballot box? In fact, the nation became entrenched in a two-party system shortly after its founding.

Here's how fundamental disagreements over the role of the federal government and a winner-takes-all system drove American politics towards a two-party system.

In laying out the framework for the government of the new United States in 1789, the Constitution made no mention of political parties. Many of the nation’s founders deeply distrusted such partisan groups. Alexander Hamilton called parties “the most fatal disease” of popular governments, while George Washington warned in his farewell address in 1796 that political factions would lead to a “frightful despotism.”

By that time, however, factions had already begun forming in the young nation. During Washington’s presidency, political elites divided themselves into two opposing camps:  Federalists, led by Hamilton; and Anti-Federalists (or Democratic-Republicans) headed up by Thomas Jefferson. These two factions sparred bitterly over how powerful the new federal government should be relative to the states, as well as whether the United States should align itself with Great Britain or France.

“I think the expectation and the hope was that you could design a government in such an ingenious way, with separation of powers et cetera, to produce policy for the common good,” says Sam Rosenfeld, associate professor of political science at Colgate University. “That presupposes that there are policies that everybody would agree is the best.

“But in fact, people disagree.”

The election of 1800, in which Jefferson defeated John Adams, marked the beginning of the end for Federalism, which had effectively disappeared as a political movement by the end of the War of 1812. That period, during the presidency of James Monroe, has been called the “Era of Good Feelings” due to the relative lack of national party divisions.

“For a little while, you get all democratic decision-making happening within the broad rubric of this one Democratic-Republican party,” Rosenfeld says. “But the disagreements haven't gone away at all. Indeed, the same kind of disagreements—about the role of the federal government and the strength of the federal government versus states—reemerge.”

The election of 1824, in which John Quincy Adams won the presidency despite receiving fewer votes in the popular election than Andrew Jackson, was a pivotal moment. Jackson’s supporters (led by Martin Van Buren) formed a new coalition based on Jeffersonian ideals that became the Democratic Party. In 1828 and 1832, the party successfully rallied behind Jackson in elections that saw many of the aspects—including campaign rallies and nominating conventions—that characterize modern-day party politics.

Meanwhile, those who opposed Jackson’s policies came together to form the Whig Party, which hewed closer to the Federalist tradition in favoring a more powerful central government. The Whigs collapsed by the 1850s, and a new anti-slavery Republican Party emerged to clash with the Democrats. Though their alignments and positions have shifted significantly over the years, the two parties have remained dominant in the United States ever since.

To understand why the two-party system is so firmly entrenched in the United States, it’s important to understand how the nation’s elections work. The U.S. system of representation is based on who wins the most votes in each district, not necessarily a majority of votes cast. In addition, each distinct area—whether congressional district, state or, in the case of the presidency, the nation as a whole—is represented by a single member, rather than proportional representation based on the number of votes received.

The tendency for such a winner-takes-all, single-member district system to promote a two-party organization is sometimes explained by a concept known as “Duverger’s law,” named after the French political scientist Maurice Duverger.

“A lot of comparative political scientists will say it's not actually a hard and fast law, but it's a good rule of thumb [that] single member districts and plurality elections tend to produce stable two-party systems and make it very difficult for third parties to emerge,” Rosenfeld explains. “The reason being: People are strategic in their voting. Faced with multiple candidates in a system in which all you need is the most votes to win, people worry if they vote for their favorite candidate that's just going to serve as a spoiler, and might perversely lead to the election of their least-favorite candidate.”

As a result, people tend to vote for their most preferred electable candidate, which is almost invariably (in the United States) either a Republican or a Democrat. The U.S. primary process, Rosenfeld says, also channels conflict over policy within each party, ideally producing general election candidates that can appeal to the broadest possible coalition of voters.

“That same kind of conflict usually generates new parties elsewhere,” Rosenfeld says, referring to multi-party systems with proportional representation, like those of many European countries. “Here, it gets channeled internally.”

Because of these structural features, among other reasons, the two-party system has remained durable through the past two centuries of American history—despite whatever public opinion polls (like this 2022 Pew Research Poll) may say about its popularity.

“I try to impart to students and other people [that] if you are really committed to wanting more choices, and you're dissatisfied with two-partyism, you need to think much more seriously about actually changing the rules of the American constitutional system, and certainly our electoral systems,” Rosenfeld says. “It's not just a question of finding a really charismatic third candidate.”