Investors are expressing concerns about potential nominees for the Federal Reserve chair, particularly those who might be appointed by Donald Trump. These worries stem from fears about the nominee's impact on monetary policy independence and economic stability.

In an extraordinary break from the diplomatic restraint typical of central banks, a dozen leaders of the world’s foremost monetary institutions issued a joint statement in January declaring their “full solidarity” with the US Federal Reserve and its embattled chair, Jerome Powell. “The independence of central banks is a cornerstone of price, financial and economic stability in the interest of the citizens that we serve,” they wrote. The move was intended to shore up the separation of monetary...