The Politics of Population Density

Swing voters in suburban communities, neither rural nor urban – will have a very decided impact on who prevails on November 8th


There are multiple ways to slice and dice the American electorate. The connection between population density and voting behavior deserves more consideration.

A Bloomberg/City Lab analysis suggests that a political tipping point between the parties occurs at about 700 people per square mile. Their conclusion: “Most of the red counties have densities of fewer than 500 people per square mile. Purple counties are clustered at between 400 and 1,500 people per square mile. And the blue counties are those above 1,500 people per square mile.” [i]

Another approach to election data concludes that an individual’s probability of identifying as a strong Democrat drops by 12 percentage points if they live in an outlying rural area. Likewise, this analysis suggests that those in a densely packed community are about 11 points more likely to identify as a strong Democrat.[ii]

In a 2019 academic paper on the “suburbanization of the Democratic Party,” David Hopkins theorizes that: “Over the past three decades, the Democratic Party has become mostly suburban in both the residence of party supporters in the mass public and the composition of its congressional caucus. This transformation reflects migration patterns among American citizens, partisan shifts among some suburban voters, and a serious relative decline over time in the party’s rural strength.”[iii]

Writing about the 2020 election, Amy Walter of the Cook Report also noted that “density was the dividing line between blue and red suburbs.”[iv] [v] Walter’s observation highlights vital clues for the 2022 elections. 

This density divide is reflected in Maryland. The most reliably Democratic jurisdictions are Baltimore City, Montgomery, and Prince George’s Counties.  And they are also the most densely populated.   The next three most dense counties, Baltimore County, Howard, and Anne Arundel are each important swing jurisdictions.

      Population Density              County / Population
1. 6,760.1/sq mi                      Baltimore City, MD / 622,271
2. 1,982.6/sq mi                      Montgomery, MD / 1,005,087
3. 1,773.7/sq mi                      Prince Georges, MD / 884,764
4. 1,199.4/sq mi                      Baltimore, MD / 817,720
5. 1,181.0/sq mi                      Howard, MD / 299,269
6.  936.2/sq mi                        Anne Arundel, MD / 550,269
7.  471.0/sq mi                        Harford, MD / 248,029
8.  369.8/sq mi                        Carroll, MD / 167,399
9. 358.5/sq mi                         Frederick, MD / 239,253
10. 318.6/sq mi                       Washington, MD / 148,913
11. 260.2/sq mi                       Calvert, MD / 89,793
12. 250.8/sq mi                       Wicomico, MD / 100,376
13. 243.6/sq mi                       Cecil, MD / 101,803
14. 234.8/sq mi                       Charles, MD / 150,960
15. 172.1/sq mi                       Allegany, MD / 73,976
16. 141.9/sq mi                       Saint Marys, MD / 108,472
17. 100.5/sq mi                       Caroline, MD / 32,759
18. 94.8/sq mi                         Queen Annes, MD / 48,439
19. 79.5/sq mi                         Talbot, MD / 37,894
20. 74.2/sq mi                         Worcester, MD / 51,558
21. 48.4/sq mi                         Kent, MD / 20,016
22.45.7/sq mi                          Garrett, MD / 29,945
23. 42.9/sq mi                         Somerset, MD / 26,197
24. 33.2/sq mi                         Dorchester, MD / 32,614

A county-focused approach misses the wide density variations within counties.   For example, within Montgomery County, one census tract, 7056.02, is the densest in the state, with the equivalent of nearly 88,000 people per square mile, while the 52 square miles of zip code 20837 averages just 35 people per square mile.

Outside of those two extremes, and more politically significant, one-third of Howard County’s population is concentrated in Columbia’s 32 square miles. Nearly 30% of Frederick County’s population is in Democratic-leaning Frederick City.  Both of these two communities have densities well above both Montgomery’s and Prince George’s averages.     

Possible explanations for a suggested connection between density and political leanings are open for speculation.    Indeed, the principle that “correlation does not imply causation” refers to the inability to legitimately deduce a cause-and-effect relationship between two events or variables solely based on an observed association or correlation between them.

Nevertheless, in Maryland and nationally, swing voters in suburban communities, neither rural nor urban – will have a very decided impact on who prevails on November 8th.