Former Trump campaign chairman Paul Manafort leaves the federal courthouse in Washington on Feb. 14. (Shawn Thew/EPA-EFE/Rex/Shutterstock)

WHEN PAUL MANAFORT, former campaign chairman to President Trump and current convicted felon, failed to cooperate with federal prosecutors in his first fraud trial, Mr. Trump called him brave for refusing to “break.” That raised a question: What was the president worried Mr. Manafort might reveal? Friday brought reason for the rest of us to hope to find out the answer.

Prosecutors from the office of special counsel Robert S. Mueller III disclosed that Mr. Manafort agreed to cooperate with them in return for leniency on his second round of charges. The White House briskly dismissed Mr. Manafort’s guilty plea as unrelated to the president’s 2016 campaign. Well, maybe, maybe not.

The charges stem from Mr. Manafort’s years of sleazy work for anti-democratic forces in Ukraine and the laundering of vast quantities of dirty proceeds. Those misdeeds do not implicate Mr. Trump. But it is unclear what Mr. Manafort offered the special counsel’s office to avoid another trial; given Mr. Mueller’s writ, it seems likely to involve Russia’s interference in the 2016 election. Mr. Manafort’s cooperation agreement requires him to submit to interviews, provide documents and testify “in any and all matters.”

Whatever Mr. Manafort reveals, his guilty pleas make him the latest in a string of senior Trump aides to admit to breaking the law — a list that also includes the president’s former personal lawyer, his former national security adviser, his former deputy campaign chairman and a former foreign policy adviser. That Mr. Trump surrounded himself with criminals shows he is either an incompetent judge of character or he values loyalty over probity. Is this what he meant when he promised to hire only the best?

In the past, critics accused the special counsel of pursuing Mr. Manafort only because of his connection to Mr. Trump. With the release Friday of even more details of Mr. Manafort’s crimes, it is clear this was no unfair prosecution. The special counsel found that Mr. Manafort smuggled millions in ill-gotten foreign money into the United States and schemed to influence U.S. policy toward Ukraine without revealing he was at the time an agent paid by the Ukrainian government. The real issue is why Mr. Manafort was not charged long before he became Mr. Trump’s campaign chairman.

Post columnist Catherine Rampell provided a possible answer last month, pointing out that white-collar crime is being increasingly ignored.

“Federal prosecutions of white-collar crime — a category that includes tax, corporate, health-care or securities fraud, among other crimes — are on track this year to reach their lowest level on record,” a record that dates to 1986, she noted. “Yet we have little reason to believe actual levels of such crimes have decreased.” Part of the problem is a distracted Justice Department, and another is the congressional GOP’s chronic underfunding of the Internal Revenue Service, which is sending fewer and fewer referrals to Justice prosecutors.

If Team Trump wants to show that it disapproves of Mr. Manafort’s lawbreaking, it could start by injecting new energy into enforcing the law. How many more Paul Manaforts are defrauding the American people right under the government’s nose?