So, what’s being sold here? Trump gave a big number, $1.5 trillion. But a leaked draft of the plan says that it will involve only $200 billion of federal money. The rest is supposed to be induced spending from private investors. That’s quite a trick. How does it work?

The answer is, basically, that it doesn’t. Private investors won’t spend on public infrastructure unless guaranteed a return. This only works if they’re given ownership, and the ability to collect future revenue from the public.

First point: lots of infrastructure just can’t work that way. There’s no way to turn sewer systems, protective levees on rivers, and lots of other stuff into profit centers.

Second, even where it does work — say, on toll roads and bridges — that private investment doesn’t come free; it’s in return for the ability to collect fees from the public, which is just taxation in another form. And there’s no evidence that doing public investment this way saves any money. On the contrary, it usually ends up costing taxpayers more than just having the government build the thing.

Wait, it gets worse. Where does even the $200 billion come from? It’s not at all clear that it’s new money; much of it would probably be money that would have been spent on public projects anyway.