WASHINGTON -- Under the unusual circumstances surrounding his selection, Supreme Court nominee Brett Kavanaugh should have agreed to recuse himself from deciding cases involving the investigation of President Trump. The reason Kavanaugh asserted at his confirmation hearing for refusing to make such a pledge -- that it would violate the imperative of judicial independence -- is entirely unconvincing.

In turn, senators should decline to approve Kavanaugh's nomination unless he does so. And, since that's not likely to happen, in the event that a case involving the Trump investigation were to come before a Justice Kavanaugh, he should not participate -- for his own good and the good of the institution he is poised to join.

The unusual circumstances are these: The president selected a Supreme Court nominee while caught up in an investigation by a special counsel. The nominee he chose happened to be one who has expressed clear -- and controversial -- views about the wisdom of investigating a sitting president.

In addition, that nominee suggested that the leading case on the president's responsibility to comply with a subpoena, U.S. v. Nixon, "maybe ... was wrongly decided -- heresy though it is to say so." Finally, although I wouldn't go so far down this conspiracy rabbit hole myself, the nominee did not appear on the original lists of potential Supreme Court choices; his name was only added to a list released after the special counsel investigation was launched.

In short, this nominee -- with this background, at this moment -- should not sit on any cases directly concerning the president's criminal jeopardy.

I don't necessarily fault Kavanaugh for declining to rule from the witness chair on the complex legal issues raised by the Trump investigation, including whether a president can pardon himself or be compelled to comply with a grand jury subpoena.

Still, Kavanaugh's comments about U.S. v. Nixon -- and his effort at the hearing to portray himself as the ruling's biggest fan -- opened the door to questions on the topic, and Kavanaugh could have been more specific. Vague reassurances about presidents not being above the law don't cut it. Neither do assertions about the supposedly bright line between policy prescriptions and constitutional judgments. A justice who has concluded, after investigating one president and serving another, that the chief executive should not be subject to a criminal probe or even civil lawsuit cannot help but have that assessment color his constitutional analysis.

But my bigger beef is with the refusal to recuse. Being a Supreme Court justice means that no one is the boss of you when it comes to deciding whether a conflict of interest prevents you from hearing a particular case. But justices follow the basic requirement to step aside "in any case in which the judge's impartiality might reasonably be questioned."

How can anyone argue that this standard is not met here? This is not to suggest that Kavanaugh would be corruptly inclined to favor Trump, or even to say that Trump named Kavanaugh precisely because of his views on presidential investigations. It is to say that the public would "reasonably" question whether Kavanaugh was tapped for that reason. You don't have to be paranoid -- you just have to be conscious -- to suspect this president of ill motives and a willingness to manipulate the legal system.

Kavanaugh's answer boils down to: It's too early to say, and it would compromise my independence if I tipped my hand. "If I committed to deciding a particular case, which includes committing to whether I would participate in a particular case, all I would be doing is demonstrating that I don't have the independence of the judiciary," he said. "All of the nominees who've gone before have declined to commit because that would be inconsistent with judicial independence."

Of course, many of the nominees who've gone before have provided assurances about removing themselves from cases in which they had a financial conflict or on which they had worked in a previous incarnation, without tainting their independence. As Kavanaugh suggested, those were more traditional, more automatic cases of recusal; still, they underscore the importance of obtaining pre-confirmation assurances. And no nominee has previously confronted this uncomfortable confluence of presidential self-interest with the nominee's on-the-record views.

It is easy to see how a Kavanaugh recusal would infuriate Trump, given that he is still railing about Attorney General Jeff Sessions. But eroding the independence of the judiciary? By contrast, recusing himself -- and doing it now -- would underscore that Kavanaugh will not risk being, or being seen as, the lackey of the president who appointed him.

(c) 2018, Washington Post Writers Group