For those who routinely stay updated about US politics, it is quite common to hear comments or read analyses about the concept of "polarization".
According to a 2022 study conducted by the Carnegie Endowment for International Peace, the United States are the most exposed democracy to the phenomenon of polarization. On a scale from 0 to 4, the US polarization index is at 3.8. As is known, it is very difficult for Democrats and Republicans to be able to dialogue or find a common agreement, even on issues of transversal interest.
Some facts are now taken for granted: the Democratic Party is very strong in the cities, while the Republican Party has a large advantage in rural areas; the Democratic Party finds a lot of support among minority voters, while the GOP still has a moderate advantage among white voters; support for Democrats grows as median income and level of education increase, vice versa for Republicans.
Although the Democratic Party has won the popular vote in 5 of the last 6 presidential elections, it has only managed to elect its candidate on 3 occasions. Because of the way the US electoral college works, the Republican Party has a structural advantage that it has managed to exploit over the past two decades, most notably in George W. Bush's first presidential election against Democratic candidate Al Gore and Donald Trump's victory over Hillary Clinton in 2016. The structural advantage of Republicans in the electoral college translates into an even greater advantage in the district college. Democratic Party voters are highly concentrated in the cities, while those of the Republican Party are well distributed in rural areas (generating that red tide effect that you can see at every presidential and congressional election, and which you can also see in figure 1).
Figure 1: click on the image to navigate the map.
The Equity Research Institute of USC Dornsife, in collaboration with the US magazine The Atlantic, analyzed data from a five-year summary by the American Community Survey of the US Census Bureau, to identify the factors behind the phenomenon of polarization in US politics. The Census Bureau summary covers a period of 5 years, up to 2020, and is therefore prior to the last redistricting. The boundaries of the congressional districts make it possible to study the composition of the penultimate US Congress, the 117th.
The two factors that mostly influence the election of a candidate of one party in a congressional district are the percentage of non-white people and the percentage of college graduates residing in that district congressional. The classification of seats in the House of Representatives (the lower house of the US parliament) based on these two variables produces the Four Quadrants of the House of Representatives (figure 2).
Figure 2: click on the image to navigate the chart.
The four quadrants are labeled as High-High, Low-High, Low-Low, and High-Low. The first quadrant (in the Cartesian orientation, therefore the one at the top right) - Hi-Hi - is that of the districts with a percentage above the national average (32.9% in 2020) of college graduates and with a percentage above the national average (39.9% as of 2020) of non-white residents. The second quadrant - Lo-Hi - is for districts with a percentage above the national average of college graduates and below the national average of nonwhite residents. The Hi-Lo quadrant mirrors the Lo-Hi, while the Lo-Lo quadrant mirrors the Hi-Hi. The visual impact of the graph in figure 2 gives an immediate measure of the profound diversity of the congressional districts in which the Republican and Democratic parties gather most of their support.
64% of the total seats of the Republican Party in the House of Representatives belong to the Lo-Lo quadrant (the third, still in the Cartesian orientation, in figure 3). 136 seats out of 213. According to the Atlantic, the GOP's heavy reliance on districts in the Lo-Lo quadrant is an emblematic index of the great shift from President Reagan-era policies to the perennial culture-war that began under the Trump presidency onwards. In the Lo-Lo quadrant, it is not surprising to find Georgia's 14th district, which elected Marjorie Taylor Greene; Florida's first district, which elected Matt Gaetz; or the third district of Colorado, which elected Lauren Boebert (that won a very tight election in the last midterm). Greene and Gaetz’s districts are well below the national average, while Boebert’s Colorado 3rd (31.8% college graduates and 30.1% non-white residents) borders the Lo-Hi quadrant. The third district of Colorado unsurprisingly is the one most in the balance among the three. Republicans dominate the Lo-Lo sector with a 10-to-1 ratio. Among other things, the third quadrant, with its 159 seats (37% of seats in the House), is also the most crowded. Here there is the structural advantage of the GOP over the Democratic Party.
Figure 3
Conversely, the Democratic Party has an advantage over the Republican Party in the other three quadrants, but the dominance of the GOP in the Lo-Lo quadrant mirrors that of the Dems in the Hi-Hi quadrant (figure 4), which is the one of the districts with high percentages of college graduates and highly ethnically diverse. Out of the 84 seats in the first quadrant, 71 are occupied by democratic representatives (84.5%). However, this quadrant weighs in at only 32% of overall Democratic Party seats. These are the districts of Alexandria Ocasio-Cortez, elected in the 14th district of New York; current House Democrat Minority Leader Hakeem Jeffries, elected in New York's 8th District; former speaker Nancy Pelosi, elected in the 12th district of California. A further element characterizes the districts of the Hi-Hi quadrant: in most of them, the median household income is above the national average ($64,944 per family, as of 2020).
Figure 4
In the other two quadrants, the advantage of the Democrats in the 117th Congress is less evident (figure 5). These are the districts that more than others have elected candidates from opposing sides in recent years, especially those belonging to the Lo-Hi quadrant (below-average percentages of non-white residents and above-average percentages of college graduates). In the 114th Congress, elected in 2014, Republicans held 49 seats out of the 88 that then made up the Lo-Hi quadrant. Of the 435 US districts, 252 are above the national average of white residents. In 236 of these 252 districts, the percentage of college graduates is less than 50%: Republicans elected in this sector of the Four Quadrants (between the low end - according to the vertical axis - of the Lo-Hi sector and the entire Lo-Lo sector) 179 representatives. To obtain a majority in the House at each congressional election, it would be enough for the Republicans to elect a further 39 representatives in the remaining part of the Four Quadrants. They succeeded in the last midterms, but it's not easy. The GOP's reliance on the Lo-Lo sector is growing stronger and increasing over the years as the United States becomes an increasingly ethnically diverse country and the percentage of people with college degrees enhances every year.
Figure 5
According to the Cook Political Report index, which assigns a rating to the 435 US congressional districts, only 21 are currently Toss-Ups, therefore in the balance. Twelve are currently occupied by Democratic representatives, and nine by Republican representatives. Of these 21, as many as 10 belong to the Lo-Lo quadrant, and 7 of these 10 are currently occupied by Democratic representatives. It is not difficult to imagine that in the future (or perhaps already in the next elections scheduled for November 2024) a part of these seats will be held by the GOP, increasing the party's advantage in the third sector of the Four Quadrants.
However, the most surprising data from the Census Bureau summary concern the disconnection of the American electorate from economic issues. Until a few years ago the single issue that most influenced the choices of US citizens at the polls seemed to be the economic policy proposed by the candidates, or the economic strength of the United States during the last presidential term. Now the factor that binds the most voters to one of the two parties is cultural affinity. In the 117th House of Representatives, 197 of 435 seats represented districts with a median household income above the national average of about $65,000 (figure 6). Democrats held 131 of those 197 seats (66%). Considering that the economic agenda of the Democratic Party is historically linked to the redistribution of wealth and that, conversely, the Republican Party has pursued a policy of detaxation over the years, the figure appears even more surprising. Although the Republicans represent 147 of the 238 seats in which the median household income is lower than the national average, they continue to propose cuts to federal programs that mostly favor their electoral base’s demographic segment and to encourage tax cuts that benefit the wealthier.
Figure 6
These contradictions exacerbate the dialogue between the opposing fields of US politics, increasing the polarization index and jeopardizing the agendas of the administrations, whether Democratic or Republican.
Edited by: Ritaja Kar