With the newswires reporting the prospect — likelihood, some say — that President Trump’s business empire will be indicted next week in New York, we recommend reading Robert Jackson’s famous speech about prosecutors. The future Supreme Court justice delivered it in 1940 at Washington, where he was serving as FDR’s attorney general. He sought to warn a room full of prosecutors of their “most dangerous power.”

It follows, Jackson said, from the prosecutor’s obligation to choose his cases. It follows, he added, that he can “choose his defendants.” The danger that vexed Robert Jackson is that a prosecutor could “pick people that he thinks he should get, rather than pick cases that need to be prosecuted.” And it looks to us as if Mr. Vance’s pursuit of President Trump is a textbook case of what Jackson warned against.

Said Jackson: “With the law books filled with a great assortment of crimes, a prosecutor stands a fair chance of finding at least a technical violation of some act on the part of almost anyone. In such a case, it is not a question of discovering the commission of a crime and then looking for the man who has committed it, it is a question of picking the man and then searching the law books, or putting investigators to work, to pin some offense on him.”

Fast forward to the Trump case. News that the Trump Organization expects to be indicted emerged after Mr. Trump’s lawyers met Thursday with prosecutors under the Manhattan district attorney, Cyrus Vance. Prosecutors have reportedly been looking at fringe benefits the Trump Organization awarded an executive, Allen Weisselberg. Yet the idea that this is what is animating the vast investigation of Mr. Trump strains credulity.

A lawyer for Mr. Trump, Ronald Fischetti, is being quoted in, among other places, the Daily News as saying that in more than 50 years of practice, he has never before seen the DA “target a company over employee compensation or fringe benefits.” Mr. Fischetti is quoted by the News as saying the Trump Organization would plead not guilty and file a motion to dismiss the indictment.

We wish him luck. The idea that the Manhattan DA is suddenly on a tear about fringe benefits strikes us as ridiculous. Cyrus Vance wouldn’t give two cents for a case about fringe benefits awarded to a single aide. No, the fringe benefits bit is, as even the New York Times reported, “part of an effort to pressure” Mr. Weisselberg “to cooperate with a broader inquiry into Mr. Trump’s business dealings.”

Prosecutions trying to, in effect, extort individuals to cooperate in a criminal investigation happen all the time, of course, but that doesn’t make it any less shocking. It has long been seen by partisans of due process as an abuse. To gain a feel for it we keep coming back to Robert Jackson’s speech. He was addressing a room full of federal prosecutors at the Justice Department, but he might as well have been talking directly about Cyrus Vance.

Jackson warned of “times of fear or hysteria” when “political, racial, religious, social, and economic groups, often from the best of motives, cry for the scalps of individuals or groups because they do not like their views.” The idea that the Democrats baying for Trump’s scalp during the past four years were operating from “the best motives” strikes us as a bit naive 80 years after Jackson gave his speech.

The future Supreme Court justice, himself a Democrat, did make a particular warning about “subversive activities,” but he wasn’t talking about just communists and the like. He reminded his audience that the terms “Republican” and “Democrat” were themselves once seen as “epithets with sinister meaning.” He stressed the danger of “factional purposes,” a point to remember as an elected Democratic prosecutor goes after President Trump.