US President-elect Donald Trump has repeatedly threatened to fire the chair of the US Federal Reserve, Jerome Powell. Up until this week, that may have seemed like a distant and outlandish prospect. Now, we again have to take it seriously. Powell himself certainly is – and has already begun pushing back on the front foot. Responding to the threat on Thursday, he insisted he will not resign. Further, he said any attempt by Trump to remove him was “not permitted under the law”. Whether Trump actually attempts to follow through on his threat will provide an early litmus test of…