DID ACTING attorney general Matthew G. Whitaker examine the memo that special counsel Robert S. Mueller III released Tuesday? Has he seen the material that Mr. Mueller redacted from the document? Has he sought the advice of Justice Department ethics experts on how much he should be involved in the Russia investigation? If so, what did those experts say?

A month into Mr. Whitaker’s reign as the nation’s chief law enforcement officer, these and other questions remain unanswered. A Justice Department spokeswoman declined to answer when we put them to her on Wednesday. Also mysterious is when President Trump intends to nominate a permanent attorney general. The White House did not respond when we asked. And then there’s the still-contested question of whether Mr. Whitaker’s appointment violated the Constitution.

All of these questions matter, because Mr. Mueller’s investigation continues, and Mr. Whitaker had previously attacked the probe. His past statements alone would raise questions about his judgment and the reasoning behind Mr. Trump’s desire for him to lead the Justice Department. Though Deputy Attorney General Rod J. Rosenstein remains in charge of the Mueller investigation, it is unclear whether the acting attorney general has butted in or intends to. Senators have pushed to pass a bill that would protect Mr. Mueller from improper firing, the approval of which would send a message to Mr. Trump and Mr. Whitaker to keep their hands off. But Senate Republicans have blocked it, and Mr. Whitaker might find subtle ways of undermining the probe.

Mr. Whitaker does not belong at the top of the Justice Department, regardless of his stance on Mr. Mueller. His résumé would be thin even for an inferior post at the department. His past involvement with a company the Federal Trade Commission accused of being a scam raises further red flags. He holds crackpot views on judicial power. His primary qualification seems to be that he gets along with Mr. Trump and other White House staff, while Mr. Rosenstein, whom the Senate has vetted and who should be running the department right now, does not. There is a reason the Constitution bars the president from appointing anyone he wants at any time to top executive-branch positions: to prevent the Mr. Whitakers of the world from suddenly controlling one of the most powerful governmental organizations on the planet.

Yet, if the Trump administration’s view of the law holds, Mr. Whitaker could wield the powers of the attorney general’s office for most of the rest of Mr. Trump’s term. Senate Democrats are upset at the lack of vetting, sending a letter to the department on Tuesday noting that ethics officials only just got through certifying Mr. Whitaker’s financial disclosures, and that “the Department has not produced prior versions of Mr. Whitaker’s financial disclosures, any ethics agreements he entered into with the Department, or any other ethics-related counseling he has received.” Senate Republicans, on the other hand, have mostly insisted that the president will appoint a permanent replacement soon.

It has already been a month. Mr. Whitaker should not have been acting attorney general for a day. It is time the Senate demands a reasonable replacement.