Remember, the P.C.A.O.B. was set up in the wake of the Enron and WorldCom auditing disasters. Before the board’s creation in the Sarbanes-Oxley Act of 2002, there was little oversight of the audit profession at all. Auditors fought its creation and settled for it as an alternative to outright government oversight of the profession. The P.C.A.O.B. is a hybrid: It is a private-sector, self-funded (through fees paid by audited companies) nonprofit. And in the end, the S.E.C. has to approve any regulations approved by the accounting board.

That’s a lot of political oversight for a nonpolitical board, and even so, the auditing profession has sought to check the P.C.A.O.B.’s powers, as it did in 2012, as the board’s chairman at the time, James Doty, cited auditor quality problems following the 2007-09 financial crisis.

Chairman Clayton of the S.E.C. is weakening the accounting board at a particularly critical time: Even sophisticated venture capital and private equity investors are regularly surprised by the shoddy practices at pre-I.P.O. companies they oversee closely, like WeWork. What chance do ordinary investors have if auditor quality is not checked closely?

The P.C.A.O.B. is the only body that has the power to force auditors to explain their work and justify their findings. In our market system, investors have to trust that the independent auditor is truly independent — and the accounting board must enforce that standard.

Yet the P.C.A.O.B. is doing less oversight and inspection work than it once did, and key positions at the agency are unfilled. Morale is reportedly low.

And then there’s the more prosaic but no less important work of the board. Members of the auditing profession would love nothing more than to see their P.C.A.O.B. audit quality inspections get a little softer and more deferential. They wouldn’t mind having a friendlier ear on the board when it comes to patching up the holes that the P.C.A.O.B.’s inspectors expose — what is called the remediation process. They would love to have a solid majority of board members ready to vote on any new carve-out of audit requirements for companies that have a good story to tell (except when it comes to their income statements).

In short, what’s at risk isn’t a specific regulatory function of the P.C.A.O.B.; it’s the independence and the credibility of the board and its staff as a whole. If the Trump White House’s goal is to strip the P.C.A.O.B. of its power, it doesn’t have to write new rules or pass new laws. It has only to nominate board members who don’t want to exercise the power they have. That’s all it takes — and I worry it’s happening right before our very eyes.

Mr. Levitt was chairman of the Securities and Exchange Commission from 1993 to 2001.

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