WHAT SPELL WAS CAST by businessman Jonnie R. Williams Sr. to induce forgetfulness and truth-shading from Virginia Gov. Robert F. McDonnell and the man who would succeed him, Attorney General Ken Cuccinelli II? What powers of alchemy does Mr. Williams, a major campaign donor, possess that prompted those two officials, the state’s most powerful elected Republicans, to flagrantly disregard Virginia’s already flimsy disclosure laws?

Already, we have seen Mr. McDonnell strain veracity by dodging disclosure of a $15,000 donation from Mr. Williams, in payment of a catering bill, on the grounds that it was a gift to the governor’s daughter for her wedding. Facts that have emerged since that claim suggest that the money was a straight-out contribution to the governor, who signed the catering contract.

Then it turned out that Mr. Cuccinelli, the presumptive Republican candidate for governor, somehow suffered a multi-pronged amnesia attack that led him not to report more than $5,000 in contributions from Mr. Williams, owner of a firm that makes dietary supplements. Among other things, the money paid for Mr. Cuccinelli’s summer vacation last year; a catered Thanksgiving dinner in 2010 for the attorney general and his family; and a flight to New York.

Now The Post’s Rosalind S. Helderman and Jerry Markon report that the FBI is looking into the relationship between Mr. McDonnell, his wife, Maureen, and Mr. Williams — specifically, whether Mr. Williams plied Maureen McDonnell with previously undisclosed gifts, presumably in return for the first couple’s help in plugging Mr. Williams’s company. (She spoke on the firm’s behalf at an industry event in Florida and hosted an event at the Executive Mansion in Richmond, at which the governor also spoke, marking the unveiling of its signature product.)

As for Mr. Cuccinelli, he finds himself in a rapidly thickening ethical morass related to the whistle-blower who first alerted federal and state authorities to the McDonnell-Williams back-scratching. In what appears to be a flagrant conflict of interest, Mr. Cuccinelli — who has counted on Mr. Williams for gifts and travel and Mr. McDonnell for political support — gave the green light to embezzlement charges against the whistle-blower, Todd Schneider, former top chef at the Executive Mansion.

Here we have the attorney general of Virginia, who aspires to be governor, prosecuting the chief tormentor of two of his most important patrons. That’s not just a failure of common sense on Mr. Cuccinelli’s part; it’s an ethical lapse.

Under pressure, Mr. Cuccinelli announced Friday afternoon — when relatively few were likely to notice — that his office would now recuse itself from the embezzlement case against Mr. Schneider. He used the flimsy excuse that a former employee of the Executive Mansion, who might be a witness in the Schneider case, is now a fundraiser for his gubernatorial campaign — a fact known to Mr. Cuccinelli for months.

The troubling questions about the McDonnell-Cuccinelli-Williams affair are mounting. Did the governor and his wife accept unreported gifts from Mr. Williams in return for political favors? Did Mr. Schneider’s role as whistle-blower factor in any way into Mr. Cuccinelli’s pursuit of criminal charges against him? How could Mr. Cuccinelli not have remembered that Mr. Williams paid for his family’s summer vacation last year? Virginians deserve answers.