Used P instead of % for data header
Removed na.strings definition
Refactored and moved the title build line
Labeled x and y for a single candidate data point
Improved axis comments
Improved reference line comments
Multiple changes:

Parsed year from filename to use in paste()
Re-added the crucial na.strings setting
Made plots save to a charts subdirectory
Changed the variable "Votes" columns to "N"
WIP: Working on a better axis (and chart title)