RUTHFULLY YOURS

It was good that Mr. Biden recognized the impact of his words, she said. But “we cannot rewrite history.”

Neither can she undo the impact of her own comments during the debate—a histrionic performance likely to cost her more than the donations and improved poll numbers that she gained. She had mounted her offensive against Mr. Biden days after Sen. Cory Booker delivered a lengthy harangue focused on his pain at hearing the former vice president speak of his ability to get on with the likes of Mississippi Sen. James Eastland, who retired in 1978.

No reasonable person could have doubted Mr. Biden’s meaning—that he had in mind a time when politicians understood the value of working with everyone to achieve results. That idea Lyndon B. Johnson understood so well—that had enabled him, as Senate majority leader and president, to flatter, arm-twist and otherwise seduce opponents of civil-rights legislation into allowing it to pass.

No one considering Mr. Booker’s abysmal standing in the polls would have much doubt, either, about the impetus that had driven his operatic display, which became increasingly vague even as the senator added detail. It wasn’t that Mr. Biden was a racist. Mr. Booker hadn’t meant that at all, he insisted. He merely wanted an apology for all the pain Mr. Biden had caused.

Ms. Harris was more ambitious. She chose the debate stage for her charge against the front-runner.

In doing so she transformed her public image—the tone that had commanded so much rapt attention every time she spoke at a committee hearing. Gone was the deadly cool authority, the presence many viewers had come to admire, as she conducted her steely cross-examinations of witnesses whose misfortune it was to come before her. She had been quick, fearless, unshakable in her pursuit of answers. There was, in that serenely contained antagonism of hers, something distinctly glamorous—no small advantage, and a rare one for an aspirant to high office.

Not least, she brought to mind the kind of candidate who could take on a certain sitting president and defeat him.

But all that was before the debate transformed her into someone whose relentlessness and self-dramatization seemed to know no bounds. She now portrayed herself as hurt and haunted by memories of a childhood in which she had encountered racism—a torment, she clearly implied, in which Mr. Biden had a hand. He had after all opposed mandated busing.

Media fanfare over this hit job—admired for its strategy, its qualification as a breakthrough event—lasted several days. The result was a fast $2 million in campaign contributions and an uptick in the polls that caused Ms. Harris to shoot up—briefly—to a position nearly even with the front-runner.

The hullabaloo couldn’t, however, erase the impression of a Kamala Harris the public had never before seen, or the tone of her self-pitying attack on Mr. Biden that went back decades to the busing era. A theme, contrived for the debate show, whose blazing-in-neon opportunism far exceeded Mr. Booker’s. His moment was by now virtually forgotten—and unlike Ms. Harris’s, fated to go unrewarded.

The debate was revelatory, as debates tend to be, and among the things this one revealed was a Kamala Harris who adhered to the comfortable belief that Americans understand the tough lives of politicians, and that all’s fair in these contests. You do what you have to do.

All of which ignores the reality that America also judges candidates on matters like character and decency and truthfulness—and the likelihood that in the age of the Trump presidency, they will be more than ever inclined to do so.

Donald Trump would be the first to agree that winning is everything. It was hard not to think of him Sunday, when Ms. Harris—clearly determined to hold on to a rapidly aging debate victory—crowned her grudging half-acceptance of Mr. Biden’s apology for mentioning his relationship with Eastland, with that added thrust: “We cannot rewrite history.”

In Ms. Harris’s playbook, the front-runner was to be consigned to the ever-more-crowded hell reserved for accused racists. She wasn’t about to let him out.

True, the playbook apparently includes a rule that both Ms. Harris and Mr. Booker observed. It requires announcing beforehand that you don’t believe the competitor whose name, reputation, and life’s work you are about to savage is, God forbid, any kind of racist—before you go on to unload an assault designed to show he is exactly that.

You do what you have to do.

Ms. Rabinowitz is a member of the Journal’s editorial board.