The size of the bubble is the total number of mentions of particular words or phrases. So the bubbles tell us the importance of specific concepts in aggregate of two parties.
It's the split within each bubble that represents the relative emphasis by party. Helpfully, the bubbles are sorted from left to right with the most Democratic words on the left. This splitting uses a bar chart paradigm. The diameter of the bubble is being partitioned, not the areas of the segments.
I wanted to see this as a straight-out word cloud. In the following, I use the red-blue-purple color gradient to indicate the Republican-Democratic bias, and the size of the words to indicate the number of mentions.
This word cloud is created using the Wordle tool, advanced options. My colleague John helped me pick the colors. (By the way, I don't like the insertion of small words within large letters, like what happened here inside the O in Obama.)
Also, I'd line the colors up so that the red words are on one side, blue on the other and purple in the middle. I'd need a different tool to be able to exercise this type of control.
Please comment on the article here: Junk Charts