President Donald Trump has opened up a new front in his attack on the Federal Reserve and its chair, Jerome Powell: He says the alledged mismanagement of a building renovation project could be grounds for firing Powell.

The central bank is poised to hold interest rates steady this month, but there could be a path to cut as early as September.

Three things can simultaneously be true: that it would be reasonable for the Federal Reserve to cut interest rates; that its headquarters renovation is too expensive; and that the Trump administration's attacks show why central banks are designed to be independent in the first place.