Actually, if a lot of people decide not to buy broccoli then fewer farmers will plant it, importers will import it off season and fewer stores will stock it. By not buying it, I might make it more expensive for others to buy and thus price other buyers out of the market depending on how elastic the supply is and what quantity efficiencies are no longer available. For example, compare the price and availability of iceberg lettuce vs. arugula.
Also, Krugman, the real point is that neither broccoli nor health insurance is a power given to Congress in article I, section 8 of the Constitution no matter how important you think one or the other is.
Correct. But IMO the statement really misses a crucially important point:
If somebody doesn't eat broccoli and other green vegetables, then his HEALTH (not necessarily his health insurance) is likely to suffer. And when anybody's health suffers, the marginal effect is to make health costs go up for everybody.
So to keep health costs low, the "progressive" mindset presumably holds that the federal government has a rational basis to require that everybody engage in the specific type of interstate commerce which deals with green vegetables.
In other words, the controversy keeps boiling down to the question,
Does the federal government have the power to force people to engage in a specific kind of interstate commerce (buying green vegetables) in order to "regulate" another kind of interstate commerce (health services and/or health insurance).
To paraphrase an infamous former POTUS:
It all depends on what the meaning of "regulate" is.
In other words, is it really "regulation" of one sort of interstate commerce (health services) when the feds require somebody de novo to engage in another sort of interstate commerce (health insurance and/or vegetables). Of course not!