In the latest Times Magazine, Robert Draper profiled youngish libertarians — roughly speaking, people who combine free-market economics with permissive social views — and asked whether we might be heading for a “libertarian moment.” Well, probably not. Polling suggests that young Americans tend, if anything, to be more supportive of the case for a bigger government than their elders. But I’d like to ask a different question: Is libertarian economics at all realistic?

The answer is no. And the reason can be summed up in one word: phosphorus.

As you’ve probably heard, the City of Toledo recently warned its residents not to drink the water. Why? Contamination from toxic algae blooms in Lake Erie, largely caused by the runoff of phosphorus from farms.

When I read about that, it rang a bell. Last week many Republican heavy hitters spoke at a conference sponsored by the blog Red State — and I remembered an antigovernment rant a few years back from Erick Erickson, the blog’s founder. Mr. Erickson suggested that oppressive government regulation had reached the point where citizens might want to “march down to their state legislator’s house, pull him outside, and beat him to a bloody pulp.” And the source of his rage? A ban on phosphates in dishwasher detergent. After all, why would government officials want to do such a thing?

An aside: The states bordering Lake Erie banned or sharply limited phosphates in detergent long ago, temporarily bringing the lake back from the brink. But farming has so far evaded effective controls, so the lake is dying again, and it will take more government intervention to save it.