Choropleth Map
A choropleth map fills each geographic area with a color that represents a variable. Usually, this variable represents relative numbers or ratios.
In this choropleth map, each county is colored by its margin (D% - R%). One drawback is that we can't tell how many votes there are in each county.
Bubble Map
A bubble map is a combination of a bubble chart placed on top of a map. The bubble size is proportional to a variable that usually represents absolute numbers.
In this bubble map, each bubble's size is proportional to the number of votes from that county. One drawback is that now bubbles overlap.
Dorling Cartogram
A cartogram distorts each geographic area to directly encode a variable. A Dorling cartogram uses circles to encode the variable.
In this Dorling cartogram, bubbles no longer overlap. However, the center of each bubble no longer stays at that county's centroid.
Beeswarm Plot
The previously shown Dorling cartogram keeps each circle closes to its original geographic centroid. Similarly, a beeswarm plot also uses the same circles placed along a single axis.
In this beeswarm plot, we can quickly compare counties' margins (D% - R%) thanks to the added margin axis. The drawback is that it no longer encodes any spacial information.