Union Popularity Down

See this survey done by The Pew Research Center for the People and the Press which finds that favorable and unfavorable attitudes toward unions are about equal. These attitudes have become substantially less favorable in the last few years.

Pew doesn't say why they think these attitudes are changing. In my experience a sharp decline in something's popularity is usually associated with some malfeasance on its part. Do we suppose the decline in union popularity is associated with the failure of the unionized "big three" auto firms? Or the widely held perception that the unionized public schools are not performing? Or maybe the malign influence public employee unions are having on our political life? My guess: all of the above.