Overlooking the obvious

Since the midterm elections, there have been a number of stories about "What 'big thing' would reinvigorate the Democratic Party?" to quote the title of one of them.   There seems to be agreement that the problem is that middle-class and working-class incomes haven't been rising, but in the stories I've read no one has raised what seems like an obvious idea:  making it easier for workers to unionize (although Thomas Edsall hints at it).  Back when unions mattered, there was a good deal of research on the "union wage effect," and the consensus was that they raised wages by something like 20% on the average (more for low paid workers and less for high paid workers).  So unionization would help address the problem, and do it  without requiring taxes or spending.  

Is the lack of attention because unions have become so unpopular that it's not worth raising the issue?  In 1952, the Gallup poll asked " In the labor disputes of the last two or three years, have your sympathies--in general--been on the side of the unions or on the side of the companies?" a number of times.  After a long gap, the question was revived in 1999, and was also asked in 2002, 2005, and 2011.  Each time, a plurality said unions--the margin ranged from 3 (37% to 34%) to 18 (52%-34%) percentage points.  The average margin was 9.7% in 1952 and 10.5% in 1999-2011--the difference is not close to being statistically significant.  (There are some ups and downs, but they have no obvious pattern, so I don't show the graph).  So it seems like a pro-union effort would have a reasonable prospect of being popular with the public. 

[data from the Roper Center for Public Opinion Research]