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.

President Donald Trump’s attacks on Federal Reserve Chair Jerome Powell are so commonplace at this point that they barely register in financial markets these days. The rapidly intensifying multi-pronged efforts by Trump’s advisers to amplify and expand on Trump’s attacks are a good reason to rethink that indifference.

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.