There were cherry blossoms. There were silk and glass butterflies. There were toasts. There was an entree inspired by a California roll and a performance by Paul Simon. But before that, there was the photo op, and the fashion.

On Wednesday evening, as the Bidens hosted Prime Minister Fumio Kishida of Japan and his wife, Yuko Kishida, at the fifth state dinner of the Biden administration, Dr. Jill Biden, wearing an evening dress from Oscar de la Renta, stood with her husband to greet their guests of honor at the North Portico.

Designed by Fernando Garcia and Laura Kim, the dress flowed in a watery fade from sapphire blue to light silver and was covered in hand-embroidered floral geometric beading.

Why did it matter? It wasn’t as symbolically obvious as the cherry blossom print gown worn by Naomi Biden or Hillary Clinton’s heavy silk caftan, but in opting for de la Renta, the first lady was not simply supporting an American company that represents the melting pot myth of the country. She was connecting to a longstanding relationship: Oscar de la Renta has dressed almost every first lady since Jackie Kennedy; Dr. Biden first wore the label for her inaugural state dinner in 2022.

On a night meant to underscore another powerful relationship — that of the United States and Japan — and reaffirm the strength of that mutual commitment through political stagecraft, the label was an apt choice.

And it suggested that Dr. Biden, who has not always seemed interested in the game of fashion diplomacy, is gearing up with every means at her disposal to help amplify her husband’s message, not just as president but as the Democratic presidential nominee as he faces off against an opponent who revels in the reality TV nature of politics — complete with costumes.

The election will be fought partly in pictures, and already the pictures are starting to tell a story, at least when it comes to the women involved.

Indeed, the state dinner portrait made for a striking image coming just four days after another photo had made its own news. In that photo Melania Trump was standing next to her husband outside the Palm Beach home of the billionaire John Paulson just before an April 6 Republican fund-raiser.

While Mr. Trump was in his signature billowy blue suit and tie, Mrs. Trump was in a pink Valentino jumpsuit covered in a print of exotic blooms — not quite royal purple, but effectively the Palm Beach equivalent. Though she had been largely absent from the campaign before that evening, as well as from Mr. Trump’s many court appearances, the dress was not that of a wallflower but of someone preparing for center stage.

“Dr. Biden and Mrs. Trump are two supporting actors in a TV show that will run from now through November,” said Michael LaRosa of Ballard Partners, a bipartisan lobbying firm that has worked with the Trumps, and a former press secretary to Dr. Biden. “They have starring roles, but they bring very different styles, approaches and brands to the audience.”

Together, the two pictures served as a sort of preview, or curtain raiser for what is to come as Dr. Biden and Mrs. Trump play increasingly public roles in their husbands’ campaigns and every detail, including what they wear, matters. The vibes may be workhorse versus show horse, but each is equally effective.

After all, as Katherine Jellison, a professor of American history at Ohio University, pointed out, clothes serve as an access point to character for the watching world, one that is familiar or exciting, relatable or aspirational.

It is not an accident, for example, that on the first day of the Japanese state visit, Dr. Biden greeted Mr. and Mrs. Kishida in a black Armani dress with a keyhole neckline that she had worn several times before. Re-wearing clothes has been one of Dr. Biden’s signatures, part of the conversation around sustainability, which nods to her husband’s climate policies (not to mention the economic realities of the country). She has done so consistently over the course of the administration. To do so again at such a moment of ritual display was to double down on the point.

Nor it is an accident that, in the last month, Mrs. Trump has been edging back into the spotlight, stepping out at strategic moments in the luxury brands that are shorthand for the financial success her husband has made part of his selling point, as if to shrug in the face of the civil penalties that have been levied against him. Because she is seen so rarely, every time she appears, it has an impact. And though that has been widely interpreted as a reluctance to engage, it is also possible that is a calculated tactic.

On March 9, for example, wearing a sharply tailored white pantsuit and a black pussy-bow shirt, she joined Mr. Trump at a dinner in honor of Viktor Orban at Mar-a-Lago. (“Pretty Woman” played as she entered.) On March 19, she went with Mr. Trump to cast her vote in the Florida primary in a white Alexander McQueen shirtdress silk-screened with orchids, high-heeled Christian Louboutin pumps and a Chanel bag. And on March 30, she appeared with her husband in a ruffled black sheath by the Danish designer Cecilie Bahnsen to celebrate the 40th birthday of his lawyer, Alina Habba.

There’s little doubt that for Dr. Biden and Mrs. Trump, this is just the beginning. On April 20, Mrs. Trump will be a star guest at a Log Cabin Republican fund-raiser at (natch) Mar-a-Lago. A few weeks later, on May 1, the White House will, Dr. Biden told “CBS Mornings,” host another state dinner — this time for educators, as part of the “Teacher of the Year” celebrations.

Both events may take place behind closed doors, but the costume drama will be there for all to see.