South Korea’s political polarization led to democratic erosion, but its institutions were able to push back. Whether the United States could do the same is far less clear.

On Sept. 11, former South Korea President Yoon Suk Yeol was acquitted in a case related to a marine’s drowning death. On July 9, South Korea’s Supreme Court upheld his seven-year prison sentence for obstruction arrest attempts in 2024. Both cases stem from the several legal proceedings that followed Yoon’s threat to democracy: the declaration of martial law.

On Dec. 3, 2024, Yoon unexpectedly declared emergency martial law during a televised address. He accused the opposition-controlled National Assembly of paralyzing the government and described his political opponents as a “den of pro-North Korean forces and anti-democratic criminals.” Yoon then deployed military forces to the National Assembly and issued orders restricting political activity and the media.

But how did South Korea even get there? Political polarization had been building for years. Yoon, a conservative, won the presidency in 2022, while the opposition Democratic Party kept control of the National Assembly. The two sides clashed repeatedly over legislation, investigations, budgets, and appointments. By 2024, Yoon was portraying the opposition not as a rival party but as a threat to the nation itself. That shift is exactly what scholars warn about. As Steven Levitsky and Daniel Ziblatt argue in “How Democracies Die,” extreme polarization can create “perceptions of mutual threat.” Once politicians begin seeing the other side as an existential threat rather than as a legitimate political opponent, they can become more willing to abandon democratic norms in order to defeat them.

Political polarization and the breakdown of cooperation between Yoon and the opposition-controlled legislature helped create the conditions that led him to take such an extreme step. And his rhetoric in his televised address demonstrated that: by portraying bringing down the opposition as an attempt to “restore liberal democracy.” When looking at Nancy Bermeo’s definition of democratic backsliding as the “state-led debilitation or elimination of the political institutions that sustain an existing democracy,” it’s clear Yoon’s actions targeted those very institutions — and had his decree stood, South Korea’s democracy could have eroded further.

Here’s where the United States comes in. Political polarization is greatly threatening democratic institutions in the U.S. In Pew’s May 2026 data, 92% of Democrats and 89% of Democratic leaners view the GOP unfavorably, and 93% of Republicans and 86% of Republican leaners view the Democratic Party unfavorably. Levitsky and Ziblatt would call this the erosion of “mutual toleration,” the norm that rivals are legitimate competitors rather than enemies. Trump’s rhetoric reflects that shift. He has described Democrats as “Dumocrats,” and Jan. 6, 2021 shows where rejecting that norm can lead: Trump refused to accept his loss to Biden, and the result was an attack on the election process itself.

The difference between the two countries is how their institutions responded. In South Korea, the National Assembly voted to lift martial law only about six hours after Yoon declared it. The Assembly impeached him, and in April 2025 the Court removed him from office. In June, President Lee Jae-myung took office and prioritized institutional accountability. South Korea has since strengthened its safeguards by passing legislative amendments that restrict executive emergency powers and bar the military from entering parliament during a crisis.

The U.S. is in a weaker position. Trump has appointed several conservative justices to the Supreme Court, who serve for life, and the Court has expanded presidential control over the federal bureaucracy. It has weakened independent regulatory agencies and allowed the removal of agency heads over policy disagreements, as in decisions affecting the Federal Trade Commission. Its conservative majority has also backed strict deportation and border asylum measures, including upholding the termination of Temporary Protected Status for Haitian immigrants in June 2026. Taken together, these rulings fit what Nancy Bermeo calls executive aggrandizement, in which power concentrates in the executive through legal channels rather than a dramatic seizure.

Yoon’s martial law was a failed coup attempt, but in the U.S. the courts themselves are helping move power to the executive. South Korea shows that having checks and balances on paper is not enough. Its institutions worked because they were willing to act quickly and decisively. Unless Congress, the courts, and federal agencies are willing to use the powers the Constitution gives them, American democracy will keep eroding through executive aggrandizement rather than a single dramatic break.