The Democratic and Republican parties of the US are strongly divided, with 80% of US adults saying that voters from both parties not only disagree on policy, but also on basic facts. This should come as no surprise, as over the last decade, tension between the Democratic and Republican parties has increased; it has become commonplace to turn on the news and see the most powerful and influential members of our government engaging in petty disagreements and name-calling. When partisan polarization increases, one’s ability to tolerate opposing views and ideas decreases. The presidency and political rhetoric of Donald Trump serve as an illustration of how rising partisan polarization in the US is eroding democratic norms, threatening the stability of American democracy.

Polarization is dangerous because it can destroy democratic norms. According to political scientists Steven Levitsky and Daniel Ziblatt’s How Democracies Die, democratic norms or “soft guardrails” work to reinforce the constitution, securing democracy. The first norm identified by Levitsky and Ziblatt is mutual toleration, where actors view their opponents as legitimate and having a right to compete within the political arena. However, when mutual toleration is low, opponents are framed and viewed as adversaries, making actors more inclined to resort to authoritarian measures to defeat them. 

Polarization’s prevalence in the US has broken down mutual toleration, as demonstrated by President Donald Trump. From the start of his political career in 2015, Trump has run on the fact that he was not a politician, and he was not a part of the “establishment,” which millions of Americans were frustrated with. As a political “outsider”, Trump has been able to forgo the norms of the democratic game. We see his rejection of mutual toleration through his treatment of opponents, like Hillary Clinton, and recently Kamala Harris. During his presidential campaign against Hillary Clinton in 2016, Trump took consistent shots at Clinton’s character and record as a politician. He frames her as “corrupt” and a threat to Americans, distorting her accomplishments as Secretary of State to support his claims that she “gets richer making [Americans] poor.” These attacks aimed to delegitimize Clinton as a candidate while simultaneously advancing Trump’s platform of being anti-politician and anti-corruption. His lack of tolerance continues into his 2020 presidential campaign, where he attacked Democratic vice-presidential nominee Kamala Harris by propagating a rumor that she wasn’t a US citizen, making her ineligible for the vice-presidency. Despite this only being a rumor– a false one at that, since Kamala Harris was born in California– Trump continued to call into question Harris’s citizenship. Trump doesn’t just try to delegitimize his opponents; he tries to frame them as an existential threat to the country. During his 2024 campaign, Trump said Kamala Harris was “unfit to lead” and would “destroy” the country within a year. Levitsky and Ziblatt would argue that the framing of his opponents as threats allows Trump to justify the full use of his powers to defeat his opponents, altering the democratic game and forgoing mutual toleration.

When mutual toleration is low, it weakens the other democratic norm that secures our democracy. Identified by Levitsky and Ziblatt, institutional forbearance refers to restraint when exercising power; actors refuse to engage in actions that are technically within the bounds of the law but still push the boundaries of their power. Contrastingly, exploiting power within legal bounds with the intent of defeating the opposition is considered “constitutional hardball.” 

Trump’s second term as president seems to be full of constitutional hardballs. In just the first year of his second term, he signed 225 executive orders, signing 25 on his first day in office. Trump has weaponized executive orders to prosecute his political opponents. He issued an executive order calling for an investigation into former President Joe Biden and his administration over an alleged “cover-up” of President Biden’s mental decline. Trump cites Biden’s use of an autopen as evidence that the former president wasn’t mentally fit to run the country. President Trump has eroded, if not completely foregone, forbearance and mutual toleration in pursuit of his own agenda.   

Trump’s consistent attacks on leaders on the left demonstrate a low in mutual toleration in the US, at the highest level. Yet, polarization and low mutual toleration are not exclusive to our top politicians. In a 2016 Pew Research poll on Partisanship and Political Animosity, 70% of “highly engaged” Democrats said the Republican party makes them afraid, while  62% of “highly engaged” Republicans said the Democratic party makes them afraid. Fear and distrust are coming from both sides. These partisan tensions are amplified by Trump’s continued attacks on the left. In an interview during his 2024 campaign trail, Trump referred to Democrats as “the enemy within,” and claimed they were more of a threat to the US than adversary countries like Russia. President Trump has shifted from delegitimizing his opponents to blatantly labeling them as threats to Americans.

The harmful rhetoric that President Donald Trump has propagated against his opponents has stoked the flames of polarization. On June 14th, 2025, in Minneapolis, Vance Boelter targeted Minnesotan elected officials, shooting Senator John Hoffman and his wife, Ivette. Later that same day, Boelter then shot and murdered Representative Melissa Hortman and her husband Mark Hortman in their home. Boelter was specifically targeting Democratic leaders, confirmed by his 45-name-long “hit list” of only Democratic elected officials. This is an extreme manifestation of a society where opposition is viewed and treated as a threat.

Democracy collapses slowly as democratic norms are eroded and constitutional hardball becomes routine, but polarization accelerates that process. When Americans begin to view their neighbors as the “enemy within” or as “dangerous,” rather than as citizens with opposing views, democracy becomes delicate. Polarization erodes mutual toleration, which prompts actors to forgo institutional forbearance to defeat opponents. The erosion of both these soft guardrails threatens our democratic system because mutual toleration and institutional forbearance reinforce the laws and institutions that uphold our democratic system.