It was probably always going to be strange.

Not because Senator Kamala Harris had cut Joseph R. Biden Jr. down on the debate stage a year ago, though there was that.

Not because of any personal awkwardness between them in their first shared hours as running mates, though perhaps there was some of that, too — discernible in their half-smiles and socially distanced waves inside a Delaware gymnasium plainly smaller than the moment.

Instead, the pair’s maiden gathering on Wednesday as the presumptive Democratic nominees for president and vice president seemed almost custom designed to answer the knottiest visceral questions about campaigning for president in a pandemic:

What defines success if crowd size and had-to-be-there electricity are nonoperational metrics?

Can zingers still zing without a laugh track in the room?

If an applause line is delivered without an audience to applaud it, does it still qualify?

“My fellow Americans,” Mr. Biden said grandly as he closed his remarks and ceded the microphone, “let me introduce to you for the first time: your next vice president of the United States, Kamala Harris.”

Silence.

Ms. Harris looked down from her chair behind him, grinned and stood, clasping her hands to her heart. Mr. Biden went to take a seat as an organizer slipped a wooden box beneath Ms. Harris’s feet for extra height.

No hug, no hands held aloft in conspicuous unity. But she was on.

Quickly, Ms. Harris confirmed a longstanding consideration among Biden allies — that almost any running mate threatened to upstage him as a dynamic public speaker. And she proved herself to be a potentially versatile messenger for whatever form the fall campaign might take.

She spoke of her friendship with Mr. Biden’s son Beau, who died in 2015, when both were state attorneys general. Her voice appeared on the cusp of catching occasionally as she ticked through her biography as the child of immigrants and as a history-making elected official in California, who ascended to prosecutors’ offices and the United States Senate. (Ms. Harris is the first Black woman and first person of Indian descent to be a major party’s nominee for national office.)

She also seemed more than willing to absorb the responsibilities of many a campaign lieutenant before her: taking relentless aim at the other side.

“As somebody who has presented my fair share of arguments in court,” Ms. Harris swaggered at one point, “the case against Donald Trump and Mike Pence is open and shut.”

But a standard, rollicking running mate rollout this was not.

There was no mass crowd to salute inside, no “thank you, Florida!” — or Pennsylvania, or Michigan, or whichever swing state campaign advisers would have preferred on Day 1.

There was no overstuffed photo line where Mr. Biden could point his finger-guns and pose, no cluster of locals to high-five the new ticket.

“I wish we were able to talk to the folks outside,” Mr. Biden said at the start of his address, alluding to supporters who had come to greet the two outside the gymnasium. “But we’re keeping our social distancing and playing by the rules.”

Still, for all the oddities endemic to a mid-virus presidential campaign, Wednesday’s event amounted to a most peculiar outcome in this political age: a scene that seemed entirely plausible, even predictable, a year ago — the conventional wisdom validated, if only this once.

Since the Democratic primary season began in earnest in early 2019, many voters had anointed themselves as real-time pundits, guessing at which combination of candidates stood the best chance against Mr. Trump. Even after a searing debate exchange over busing, musings about a would-be Biden-Harris unity ticket ricocheted through union halls and school auditoriums across Iowa and New Hampshire. (In the end, Ms. Harris’s campaign collapsed before these states even weighed in officially.)

For a self-described “gut politician” like Mr. Biden — known to shake hands and shoulders and the sides of faces, if an attendee appears amenable — the evaporation of the traditional campaign trail has been jarring. Ms. Harris, who has likewise shown a capacity for in-the-room connection, will probably have few opportunities to lean on this skill set this year.

But on balance, Democrats might count themselves grateful for these political conditions. Both candidates have been known to stumble in unrehearsed settings, with Ms. Harris in particular often demonstrating a wide gap between scripted performances and on-the-fly questioning.

On Wednesday, the two seemed to have prepared diligently to fuse their respective messages. Mr. Biden nodded at Ms. Harris’s “3 a.m. agenda” — a common refrain in her 2020 bid as she talked about the issues that keep people up at night — before reverting to his standard narrative frame: restoring American decency.

“Remember?” Mr. Biden asked, recounting the white supremacist demonstrations in Charlottesville, Va., three years ago. “Remember what it felt like to see those neo-Nazis? Close your eyes.” Ms. Harris appeared to nod from her seat with her whole body.

Near the end of her own speech, Ms. Harris resurfaced the point: “Joe likes to say that character is on the ballot, and it’s true.”

When she finished, their spouses joined them on camera, masked and waving. The couples mostly stayed apart, clapping from an epidemiologically advisable remove.

They walked off together to the sound of a campaign song, “Move On Up,” and little else.