Jerome H. Powell has rarely had it easy during his tenure as chair of the Federal Reserve. Under his watch, the central bank has had to navigate through two global trade wars, a once-in-a-century pandemic, multiple geopolitical conflicts overseas and the worst inflation shock in decades.

But with just nine months to go until his term as chair is up, Mr. Powell’s circumstances have become particularly precarious.

Mr. Powell is facing relentless attacks from the White House and the recurring threat of being ousted by President Trump, while a handful of candidates openly jockey to replace him. He must grapple with all of this while managing divisions in his own ranks about when to lower interest rates again after a long pause.

The Fed is widely expected to hold interest rates steady on Wednesday for its fifth straight meeting, a decision that would undoubtedly anger Mr. Trump and add yet more fuel to a pressure campaign that has expanded beyond the central bank’s handling of the economy to how Mr. Powell manages the institution itself.

“There’s a deeper existential issue that Powell is wrestling with that goes beyond how much to cut rates,” said Mark Spindel, chief investment officer at Potomac River Capital, who wrote a book on central bank independence. “This is about being openly challenged on whether the Fed and its institutional structure should exist.”

Avenues of Attack

The lengths the Trump administration has been willing to go to try to undermine the Fed and discredit Mr. Powell were on full display in the days leading up to Wednesday’s meeting.