Is it possible that the people who run CNN.com are this sloppy?
Option 1: They were trying to honestly and accurately present their polling data in graphic form, and botched the mission spectacularly.
Option 2: They were intentionally trying to misrepresent the data. To make the party-split look more dramatic? To make Democrats look bad? To make them look good?
Whatever the reason, the verdict is the same: Terrible, sloppy journalism CNN should be ashamed of.