Outside of a U.S. President bending norms, the Fed also faces challenges in achieving its economic objectives. Inflation remains above its 2% target: Its preferred measure is at 2.4%, though core prices — considered a better gauge of where inflation is headed — rose 2.8% in November from a year ago.

Policymakers left their benchmark rate unchanged amid signs that the economy is humming along, defying the president’s tradition-bucking pressure on the central bank.

The Federal Reserve defied Donald Trump’s demands for lower borrowing costs by keeping US interest rates on hold and suggesting they will remain higher for longer...