I'm not sure if I follow the second part. Adding more comma-separated words doesn't do anything to the other lines, this is just an overlay of multiple graphs. Adding or removing 'taxes' doesn't do anything.
Sorry for not being clear (was also trying to not be verbose!). All it shows is that all those terms were searched a lot less than Romney for the past 90 days, and yet they all were found to alter subsequent search results after searching them (unlike Romney).