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.

In a letter Thursday, the Federal Reserve chief rejected criticism the White House has leveled at him over the cost of renovation projects.

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.