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.

The Supreme Court said in May that it could block any attempts by the White House to dismiss Powell, noting as part of a separate ruling that the Fed “is a uniquely structured, quasi-private entity.”...