Vice-presidential debates seldom shake up presidential races, and the face-off between Kamala Harris and Mike Pence on Wednesday night seems destined to be no different.

Both candidates had strong moments, and a few stumbles, over the course of the 90-minute affair. But as far as lasting memories go, they were few and far between.

If this was a match that showcased the futures of the Democratic and Republican parties, the real fireworks will have to wait for the coming years.

An unmemorable result, in and of itself, is good news for the Democrats and Joe Biden, who polls suggest are leading in the race. One more campaign set-piece in the books, and one step closer to election day. These are my takeaways from the debate.

A very different tone from last week

The lasting memories from last week's presidential debate are probably ones of tone and demeanour - Donald Trump's constant interruptions and Biden's occasional "will you shut up" flashes of temper.

Both vice-presidential candidates clearly had this in mind as they sat down behind their plexiglass-protected tables.

Pence's typically calm and methodical style served as a steady counterpoint to Trump's earlier aggression. On the occasions when he did interrupt, however, Harris was ready.

"Mr Vice-President, I'm speaking," she said. "If you don't mind letting me finish, then we can have a conversation."

Given the dynamic of the debate - a white man interrupting the first black woman vice-presidential candidate - those were fraught moments for Pence, where the normally placid Midwesterner risked seeming rude.

What's more, Pence had no qualms steamrolling moderator Susan Page - and given that women voters have turned sharply against the Trump-Pence ticket, the extra speaking time he gained may have come at a political price.

The format, and the candidates' reluctance to aggressively press each other, ensured that the evening would shed little new light on either side's positions or reveal how either candidate performed under pressure.

Harris fails to exploit virus weakness

Not surprisingly, the coronavirus pandemic was the opening topic of the debate - and not surprisingly, Harris spent most of her time on the attack. Pence, on the other hand, focused mostly on the defence.

Harris's sharpest line was to cite statistics - 210,000 Americans dead - and charge the Trump administration with "ineptitude" and "incompetence".

Pence had his response ready. He said the Biden-Harris plan was largely a copy of what the Trump administration was already doing, boasted about speedy progress on a vaccine and treated criticism of his administration as an attack on first-responders and US healthcare workers.

Surprisingly, neither candidate spent much time on the fact that the White House itself has become the latest coronavirus hotspot. An obvious line of attack for Harris was left unexploited and the conversation soon shifted to other subjects. Given that polls suggest handling of the virus is the Trump campaign's greatest weakness, a draw on the topic is success for Pence.

Both sides uncomfortable on climate

If Pence was on his back foot on the pandemic, when the topic turned to the environment, it was his turn to go on the attack.

Biden has expanded his plan to address climate change since the Democratic primaries. Harris was an original sponsor of the Green New Deal climate proposal, which set ambitious targets for carbon emission reductions.

While that has won them plaudits from environmentalists on the left, there are voters in swing states like Pennsylvania and Ohio who might view more government regulation as a threat to their economic livelihood.

Pence warned that the Green New Deal would "crush American energy" and accused Biden of wanting to "abolish" fossil fuels and ban fracking, which Harris said was false.

In one awkward moment, he dodged saying climate change was man-made or a threat to the planet, merely stating more than once he would "follow the science".

Biden has had to walk a fine line on the environment, however. During the debate Harris said that climate change is an "existential threat" to the globe, but both she and Biden have avoided a full-throated defence of the kind of government response that would require - lest it alienate key voters in key states.

Pence denies systemic racism

The sharpest exchanges of the entire debate came late in the evening, on the topic of race and law enforcement.

As Trump did a week earlier, Pence tried to quickly pivot from a discussion of discrimination and excessive force by law enforcement into a condemnation of the sometimes violent protests that have occurred in US cities. He said he trusted the justice system and that suggesting the nation is systemically racist is an insult to the men and women in law enforcement.

That set up Harris's most powerful rejoinder.

"I will not sit here and be lectured by the vice-president on what it means to enforce the laws of this country," the former San Francisco prosecutor and California attorney general said curtly.

She noted Trump's difficulties - as recently as the debate last week - in clearly and concisely condemning white supremacists, concluding "this is who we have as president".

Of course, there was a fly on Pence's head for almost the entirety of this moment, so that may be what everyone is talking about in the days ahead.

A look into the future

This vice-presidential debate gave the Americans who chose to watch a look at US politics present and future.

For the current election, both candidates did their best to defend their running mate and land shots on the top of the opposing ticket.

The participants in this debate were also looking beyond November, however. Pence - like most vice-presidents - has his eyes on a presidential bid of his own. To do that, he'll have to win over Trump's base while also casting a wider net to Republicans and right-leaning independents who may have become disaffected with Trumpian politics. Throughout the debate, he defended Trump, but also tried to carve out his own identity, particularly when discussing issues - like the Supreme Court - near and dear to the hearts of evangelical voters.

Harris, who at this point last year was running for president herself, tried to prove that she can be a capable standard-bearer for the Democrats once Joe Biden exits the political stage. When given the chance, she spoke about her upbringing and background, taking the opportunity to introduce herself to a larger US audience. Unlike Pence, she frequently talked directly to the camera - conscious that while she was trying to score points, it was equally important for her to connect with the audience.

Four years ago, Democrat Tim Kaine gave an unremarkable performance against Pence, and his national standing hasn't seemed to recover. Harris gave a good enough showing on Wednesday, her one big 2020 moment in the spotlight, that she at the very least will avoid Kaine's fate.

Both Pence and Harris live to fight another day - and that day could come in just four years.