U.S. President Donald Trump is set to announce his pick to chair the Federal Reserve on Friday morning, setting up a key shift in the central bank’s leadership.

Powell’s chairmanship ends in May, and the next chief will need to establish credibility despite political pressure, while walking a policy tightrope between curbing stubborn inflation and supporting a weakened jobs market.

The frontrunners for the job are former Fed official Kevin Warsh, Fed governor Christopher Waller, Rick Rieder of BlackRock and Trump’s chief economic adviser Kevin Hassett.