Unions are basically socialist constructs, huge businesses whose product is workers dues dollars. They cannot 
survive without them so they need to manipulate the business/worker environment to maximize their income earning potential.
The biggest union scam ever conceived was the public sector union. Taxpayer funded employees pay dues which are then used to influence elections at every level in favor of a political class that will then build union power by growing government, and adding more dues paying union employees whose additional funds will then keep the pro-union politicians in power.
Want to know why democrats care about public school class sizes? More teachers, more dues, more democrats. It has nothing to do with learning. Now project that thinking across the entire "grow government" universe and you have a massive scheme to swell the bureaucracy at your expense that should be illegal but is not. But with Obama serving as their Johnny Appleseed, using your money–provided by the democrat congress–he’s been creating and saving dues paying public union jobs (and democrat campaign coffers) all over the nation.
To show you how much larger a problem this is than you may have suspected look at some data compiled by the Wall Street Journal for this year’s political contributions to elections by third party groups (above). Three of the top five are national unions with AFSCME, the leader in the public sector union racket on top with over $87,000.000.00 million committed to affecting elections at every level. Combined these three unions alone have spent over $171,000,000.00 million dollars on democrats, a majority of that from public sector unions, which represent only a fraction of the population.
Unions are a special interest group, a fringe group, that enriches themselves and their agenda on the backs of the workers they claim to represent.
Carol Shea-Porters is a fine example, raking in a massive union haul from every union within reach, some of them internationals, some from locals, all beneficiaries of democrat bail outs, carve outs, handouts, and legislative policies that favor their workers who then reward democrats with more campaign dollars. It is a scam of massive proportion that exceeds most if not all corporate equivalents by leaps and bounds.
So as the democrats scramble in the closing days to nag at you about special interest money, just remember, unions are a special interest, they spend more than anyone on their partisan agenda, and in many cases, they are using your tax dollars laundered through public employees to squeeze you until you have nothing left to give.
