After Sen. Kamala D. Harris last year unleashed one of the most searing attacks of the Democratic presidential primary against Joe Biden, his wife, Jill Biden, called it the “biggest surprise” of the race. Even eight months later, the former second lady said it was “like a punch to the gut.”

On Friday, a far different dynamic was on display. Harris (D-Calif.) smiled broadly as she introduced Jill Biden as “our next first lady.” Jill Biden closed her eyes and put her hands over her heart as she recalled how Harris’s op-ed on black maternal health touched her.

The striking show of bonhomie came during a virtual discussion on the Affordable Care Act, which had all the trappings of a typical Biden campaign event. Except this one was freighted with a tense history and effectively doubled as a high-stakes public tryout — the latest in a series featuring a Democrat under consideration to be Biden’s running mate.

To some Biden allies, it also served as a visible turning-of-the-page on an uncomfortable chapter that has loomed over the vice presidential search. Seeking to quell rumblings from some Democrats who have said they detected signs of frustration with Harris from Jill Biden and Valerie Biden Owens, Biden’s sister and longtime political adviser, the Biden campaign on Friday looked to publicly dispel the notion that their views of Harris are anything less than positive.

“Both Dr. Biden and Valerie have nothing but the utmost respect, admiration and affection for Senator Harris,” Biden campaign spokeswoman Elizabeth Alexander said in a statement. “Any rumors or conjecture to the contrary are not true and have zero basis in reality or fact.”

Some Biden allies pointed to Biden’s relationship with Barack Obama, which Biden has said he is seeking to re-create with his eventual running mate. It, too, had some difficult chapters….