Jeff Sessions may have been the most effective member of the Trump Cabinet. The attorney general — until Wednesday, or one day after the midterm elections — led the way on the president’s signature issue, the reshaping of immigration policy, including steps to deter entry, both legally and illegally. For the president, that wasn’t good enough, as he long advertised. He wants an attorney general who serves first as a presidential protector.

More, the president has something particular in mind. He has berated Sessions in public and private for giving up oversight of the special counsel investigation conducted by Robert Mueller, contending he wouldn’t have tapped Sessions if he knew a recusal soon would follow.

Mueller and team have been examining the Russian intervention into the 2016 presidential election and whether the Trump campaign aided or participated in the effort. Sessions was part of the campaign. At the time, he met with the Russian ambassador. He rightly followed the advice of ethics professionals at the Justice Department who advised stepping back from the investigation, leaving oversight to the deputy attorney general, Rod Rosenstein.

The president has cited for justification Robert Kennedy serving as the attorney general for his brother, President John Kennedy. Yet that was before the Watergate scandal, and the deeper impression it made on the importance of an independent Justice Department. The Kennedys did not face anything close to the Russia matter. Surely, if they had, Robert Kennedy would have been pressed to remove himself.

President Trump has not been subtle. He advertised widely that he dismissed James Comey as the FBI director because of the advancing Russia investigation. That set in motion events resulting in the Mueller appointment. Now, as the investigation has proceeded further, with indictments and convictions, the president has struck.

The firing of Sessions means the door is open to appointing a successor without the same complications and thus in position to oversee the investigation. Yet, first, an interim attorney general is needed, and the choice the president made is telling, potentially chilling. He didn’t take the usual step of giving the job to the deputy. The president elevated Matthew Whitaker, the chief of staff for Jeff Sessions.

It just so happens Whitaker has expressed views in public about the Mueller investigation. He has discussed circumstances for limiting its scope. He said, “You would always take the meeting,” regarding the Donald Trump Jr. session at Trump Tower with a Russian lawyer trading dirt on Hillary Clinton. Many legal experts, Republicans and Democrats, disagree, arguing the FBI should have been informed.

Whitaker appears the type of attorney general the president would like. No doubt, ethics officials at the Justice Department will assess whether he should step back, for starters, because he appears to have prejudged the investigation. If they find a problem, he would do well to follow their advice, though the recommendation is not binding.

This is a fraught period, Mueller moving ahead, Democrats yet to take charge in the U.S. House. The better course would have been to make Rob Rosenstein the interim attorney general, the president then selecting a nominee who would be asked in the confirmation process to declare support for the Mueller investigation. The president doesn’t operate that way, and in doing so, he not only challenges the worthy traditions of the Justice Department. He adds to the appearance he has something to hide.