Just saw a debate centered around Linda Chavez's new book, Betrayal (popular term these days, eh?) in which Alan Colmes alleges there is no difference between corporate political donations (through political actions funds) and using union dues to support Democratic candidates.

Sounds like a reasonable argument, doesn't it? After all, just as many union members will vote Republican, so also many employees might oppose whatever party is being supported by the corporation. (I phrase it this way because I've seen corporations support Democratic candidates. I've never heard of a union supporting a Republican.)

In making this argument, Alan misunderstands some very basic economics.

First, consider a corporation: Certainly every company would love to sell its products for the highest price possible, and pay as little as posible for labor and raw materials. So why don't they? Why doesn't GM charge a million dollars for each car and pay all their workers the minimum wage, or nothing at all?

The reason is because each company doesn't exist alone, but competes in a "market" against others. On the selling end, GM competes against Toyota, Ford and others including bicycles and mass transit. On the production end, GM competes against other companies for employees and raw materials.

So the prices of an employee, or car, is set by the market, not the company: If GM tries to charge too much for a car, people will buy another brand. If they try to pay an employee too little, she will go elsewhere.

So when a company in a competitive market wants to donate money to a politician, not much can come out of employee salaries -- lest their employees go elsewhere -- and not much can come from making the product more expensive -- lest consumers buy from their competitor. So most the money must come out of profit, not the worker's salaries.

Further, if an employee really doesn't like the political cause which their company supports, he or she can often change workplaces with comparative ease.

Now consider the union: Recall that unions work by "locking up" the supply of a particular kind of worker (job description) under their control, across many employers. So while it may be easy for a public school teacher, pipefitter, or cameraman to change their place of work, it is harder to escape union control -- a powerful union will control many or most similar jobs.

Next, recall that union dues actually do come out of the worker's paycheck. This is no illusion: Since the union (when powerful) controls the entire labor pool, it takes its cut after the employees negotiate their best wage.

So there are two very important differences between union dues and corporate political donations: Unions dues really do come out of the member's pockets, and skilled workers can much more easily avoid working for a particular company than avoid working for a union.

In other words, corporate donations are generally voluntary and do not generally come from workers' salaries, where union dues are generally coercive, and are indeed taken directly out of the worker's pocket.

And that's a huge difference in my book.