One of the main chapters in Darrell Huff's 1954 book "How to Lie With Statistics" concerns how graphs and charts are ready-made tools for inflating or downplaying a political point. A textbook example is Gallup's chart showing Obama's approval rating over 2013.
http://talkingpointsmemo.com/...
Note that the X-Axis covers the range from 41 percent to 52 percent. If the chart had used zero to 100 percent on the X-Axis, the decline would not have looked nearly as dramatic.
An 11-point fall in approval is nothing to sneeze at, but is not the free-fall suggested by that downward diagonal slash.
If you haven't read Huff's classic, do yourself a favor and dig up a copy. It's a quick, enjoyable read, and every technique he described in 1954 is in daily use today.