As the Trump administration has emphasized the primacy of national interests under its “America First” banner, particularly in the areas of trade deficit with South Korea and the cost of keeping US troops there, Korea and the United States have faced many challenges and still have unsolved problems. More important, however, the United States has long been a model for Korean presidential democracy. In fact, the United States and South Korea present a substantial number of parallels with respect to their constitutional structures, electoral systems, party systems, and political situations. Among other parallels, both democracies have presidential systems. Despite disparities such as the terms of office and the rules of elections, there is no doubt that the presidents in South Korea and the United States are leading political figures, as well as the only public officials elected by the entire electorate. In addition to its presidential system, South Korea parallels the United States in its long-standing use of a single-member plurality system for legislative elections.^{Footnote 1}

An electoral system often is viewed as the primary institutional determinant of a legislative party system. A single-member plurality system has the effect of putting a higher threshold of exclusion to the advantage of large parties or manufacturing majorities, thereby facilitating the two-party system in both South Korea and the United States. In addition, the candidate-selection procedure in major Korean political parties has evolved in a more democratic direction, departing from top-down candidate selection in the past. In adopting the bottom-up method of candidate selection, major Korean parties have opened up the selection process of candidates—most importantly presidential candidates—not only to party members but also to ordinary voters as in the US primary system because most Korean political parties are lacking members who voluntarily joined the party.^{Footnote 2}

The two major parties in South Korea—the liberal Democratic Party and the conservative Liberty Korea Party—are not only dominant but also increasingly polarized in recent years. The upward trend in party polarization in South Korea is similar to US party polarization, which has developed since the Reagan Era of the 1980s and further deepened in the twenty-first century, particularly after the 2008 election of President Obama and the emergence of the conservative Tea Party movement. Consequently, there has been a notable increase in party votes in the American Congress; legislators more often support their party on party votes, frequently leading to legislative gridlock as well as executive–legislative confrontations.

These confrontations have been further exacerbated under the Trump presidency, as demonstrated by the longest government shutdown and the unprecedented delay of the State of the Union Address as a result of partisan bickering. The excessive partisan conflict is now greatly undermining governance in America. Likewise, the two major parties in South Korea are no less polarized than their US counterparts. In Korea’s National Assembly, party cohesiveness of the two major parties also is very high, frequently resulting in fierce confrontations within the increasingly polarized legislature and undermining governance. This was evident in the recent three-month-long legislative deadlock triggered by the ruling Democratic Party’s move to fast-track key reform bills.

Polarized party politics in South Korea and the United States typically leads to growing disconnect between ordinary voters and political parties. Political parties are increasingly influenced by party activists focusing on their ideological issues rather than ordinary voters’ pressing issues of daily life. Voters frustrated with establishment parties and politicians have become more vulnerable to the populist mobilization by “outsider” politicians, who often make use of inflammatory and provocative rhetoric. Korean students in American politics classes tend to view the emergence of the populist Trump presidency in part as a result of a growing disconnect between American voters and the political establishment. Given the Korean–US parallels, they also express their concern about a possible emergence of Korean populist politicians who are not accountable for their actions and who try to break or bend the law to solve political problems.

Another worrisome parallel between the two democracies is the strengthening negative partisanship aggravated by various challenges to the basic parameters of American democracy under the Trump presidency. Korean partisan voters’ negative feelings toward the opposing party and its supporters also continue to grow. According to a Gallup Korea poll (March 8, 2019), Democratic Party supporters’ dislike of the Liberty Korea Party was 88%, and Liberty Korea Party supporters’ dislike of the Democratic Party was 89%. In fact, Korean partisan voters dislike or even hate one another more than they did in the past, thereby further reducing the low level of political tolerance that is a core element underlying the workings of the democratic process. Unfortunately, political tolerance also seems to be suffering under the Trump presidency largely due to emotionally charged party polarization, which was well reflected in the clearly distinct responses of Democrats and Republicans to the redacted Mueller report.

Because of the many parallels of political systems and situations in the United States and South Korea, American politics has set—for better or worse—a type of reference structure for evaluating various aspects of Korean politics and suggesting political reforms. Moreover, a long history and accumulated experiences of American democracy with similar political systems and situations continue to provide ample precedents related to the workings of presidentialism and the challenges facing Korean presidential democracy, such as executive–legislative tensions embedded in the constitutional structure of power separation based on dual legitimacy.