Can Kamala Harris win by standing for nothing?

Self-awareness is a rare trait in a politician, so when Tim Walz described himself at last week’s vice presidential debate as a “knucklehead,” the Minnesota governor should have been applauded rather than mocked. It was a welcome moment of honesty in a short national political career that has so far been characterized by extended episodes of biographical dissimulation.

It might even have been endearing except that it came wrapped in a thick blanket of more obfuscation, bluster and diversion that left us all still confused not only about the man’s whereabouts when the Tiananmen Square massacre was taking place in Beijing, but about much more besides. I don’t suppose anyone cares where he thinks he was in June 1989, but there is something a little unsettling about the apparent compulsion on his part, as we’ve seen with claims about his military record, to place himself, like Woody Allen’s Zelig, at the center of events of world-historical importance.

Still, as things stand, he is merely a swing state and a heartbeat away from a genuinely world-historical moment. If our next vice president is to be a self-acknowledged knucklehead, then surely we have the right to know something similarly informative about the woman he might one day be called upon to replace. Yet here we are, four weeks from Election Day, and still the political identity, intellectual capacities and personal character of the Democratic candidate for president remain a riddle inside an enigma wrapped in a mystery.

This was underscored by another, unintentionally more revealing remark Mr. Walz made in that debate last week—not some blathering deer-in-the headlights response to a question, but evidently a carefully prepared and delivered part of his closing statement.

“I’m as surprised as anybody of this coalition Kamala Harris has built—from Bernie Sanders to Dick Cheney to Taylor Swift,” he said, staring into the camera. “They believe in a positive future of this country and one where our politics can be better than it is.”

The intention was obviously to illustrate the great breadth of the team that supports the vice president over Donald Trump, spanning the vast ideological territory that her campaign now commands.

But if you think about its implications for what a Harris administration might actually look like and what it might do, it supports only the impression of complete vacuity. What sort of intellectual coherence can we expect from a governing coalition of this apparent width and ideological diversity?

Set Ms. Swift aside—she fits the usual mold of Democrat-embracing celebrities. The composition of the rest of this team is very novel. Mr. Cheney is a conservative Republican with a record of passionate support for small government at home and the assertive use of U.S. military power overseas. Mr. Sanders is a “democratic socialist” who never saw a tax increase he didn’t like or a foreign adversary he didn’t have sympathy for. (Liz Cheney, Mr. Cheney’s daughter and also a Harris supporter, once described Mr. Sanders as a “commie” with “daddy issues.”)

Of course people of differing political priors, or none at all, can come together to support a candidate they regard as the less dire alternative. But when they do, the rest of us have a right to be given some sense of what they are endorsing. Endorsements by public figures are usually a useful guide to what kind of political choice we are being offered.

Say what you will about our hyperpartisan politics, but at least it offers a choice between two very different sets of ideas for the country. When one of the choices appears to contain ideological range as wide as the entire political spectrum, what exactly does that choice represent?

This would matter much less if we had any real idea what sort of political direction a Harris administration would follow—something that might make the Cheneys wince? Or something that would leave Sen. Sanders grumpy?

We don’t, and as far as we can tell four weeks from Election Day, we aren’t going to be given a chance to explore what exactly she would do on any of the issues spanned by the Sanders-Cheney axis.

When she launched her campaign in July, it was obvious that the plan was to disown all previously unpopular positions she had ever adopted and say essentially nothing about anything else. Even with 3½ months until the election, it seemed inconceivable she could be allowed to get away with it.

But the strategy of giving no press conferences and allowing interviews only with journalists who evidently support her remains intact. She did get the better of her opponent in their debate last month, but Mr. Trump isn’t the most assiduous when it comes to investigating the details of policy. This week, assuming she survives the grilling from her friends at CBS on “60 Minutes” Monday night, she has agreed to submit herself to interrogation from the ladies at “The View,” Stephen Colbert and Howard Stern.

If we learn anything valuable from any of these encounters it will be purely by accident, like an impression left on an empty chair.