For a long time, the argument against government-sponsored health care was that…well, you know. It's the government so it has to be worse and inefficient and it can't possibly be as good as what free enterprise can offer.
Suddenly now, the argument against a "public option" in health care is that hundreds of thousands of people would prefer it so they'd transfer away from private insurers and cost Aetna and Blue Shield and the others a lot of business. In other words, the problem with government-run health care is that it would probably be better. And we can't have that.