When Americans vote Tuesday for what the press is calling a referendum on President Trump, will they be buying a pig in a poke? The phrase has to do with the idea of a pig in a cloth sack, or poke (from the French “poque,” which also turns out to be the root of pocket). The phrase, Webster’s says, denotes “something offered in such a way as to obscure its real nature or worth.”

What brings this to mind is a Politico column by Jack Shafer about how the special prosecutor, Robert Mueller, has been adhering to Justice Department rules requiring him to, as Mr. Shafer puts it, “avoid actions that might influence the outcome of an election.” Yet by playing his cards so close to the vest, Mr. Mueller may be creating the problem the regulations seek to avoid.

Our interest here is with neither Messrs. Trump, Mueller, nor Shafer but rather the long-suffering American voter. As it stands, she or he will go to the polls for what is being billed as a referendum on the president, while wondering about whether he might be brought up on charges. Or recommended for impeachment. Or cleared of wrongdoing and put up for the Nobel Prize.

We exaggerate only to underline the point. Is there no way for the Justice Department to deign to share with the persons who elected Mr. Trump and gave him a Republican Congress (and pay the Justice Department’s salaries) at least some inkling of where they are headed? Has indicting the president been ruled out? Is he still, or was he ever, a target of the probe?

No doubt this is a dangerous game. Ask Hillary Clinton. There the Justice Department — or, rather, one FBI director with flawed judgment — let voters know what an investigation found, or didn’t. It ended up revising that and revising the revision. Net-net, in Secretary Clinton’s view, Justice threw the election. What, though, might someone more competent than James Comey do?

This editorial isn’t about whether President Trump is guilty. It’s merely to remark on how amazing the situation is. American taxpayers have sunk millions, probably tens of millions, into the special prosecutor’s operations. Yet on the eve of what is being called the election of a lifetime, no one in government has told them what the special prosecutor even estimates he’s got. It’s shocking.

Just to mark the point: What if Mr. Trump manages to hold on to the House and expands his position in the Senate and, a month hence, gets nominated for impeachment by Mr. Mueller? What if Mr. Trump loses both the House and the Senate only to be cleared, sometime hence, in Mr. Mueller’s final report? What is Mr. Mueller going to look like if he had a good idea of where he was heading before the election and kept his mouth shut?