The stakes were higher for Democrat candidate Kamala Harris in the US presidential debate: she has a tougher audience to win over than Republican Donald Trump does. 

The people Harris needs to persuade to vote for her are middle Americans who, until the rise of Trumpism, would rarely have countenanced supporting a Democrat.

In 2024, they don't want to vote for Trump because they don't like him. But it's a big ask for them to tick the box for a San Francisco liberal instead.

These are citizens who prefer small government, personal liberty, are allergic to the progressive left and woke-ism, and who would have comfortably voted for George W Bush in 2000 and 2004, John McCain in 2008 and Mitt Romney in 2012. They may well have even voted for Trump in 2016.

But now, after witnessing four years of Trump in office, and his behaviour out of it, they're reluctantly open to options.

The risk for Harris is that as these voters evaluate her, they will end up landing at the position espoused on the weekend by the Republican who made the best run against Trump in this year's primaries, the former US Ambassador to the United Nations, Nikki Haley.

"I don't have to like him or agree with him 100 per cent of the time to know that life for Americans would be better under the policies where we have strong immigration, where we have law and order, where we have an economy where we can look at opportunities, where we've got national security that is strong," Haley said.

A nervous start, then came the attacks

If enough people share the Haley "hold your breath and close your eyes" approach to voting — to steal a lyric from the musical Hamilton — that could get Trump over the line. 

Those guarded voters, not naturally drawn to a Democrat but no fans of Trump, are the ones Harris needs to pick up in vital battleground states such as Pennsylvania and Michigan if she hopes to win.

So how did she do with that mission in the debate?

Fine, but Trump held his own and managed to ram home some of the points that will hurt her the most with wavering voters: the economic pain they feel, problems with border management during the Biden administration, and the fact she has already had four years close to the centre of power.

The most notable visual came right at the start, as the two candidates took the stage.

Harris walked directly across to Trump's podium, extended her hand and introduced herself.

She appeared confident and on the front foot, but as with all things political, it's a Rorschach test — Trump supporters may have thought she seemed deferential by moving to his turf while he took the podium presidentially.

Harris had a nervous start, clearly discernible in her speech, showing signs of a dry mouth, anxious swallowing and a quaver at times.

She began with an economic message, acknowledging that Americans are finding the cost of living arduous and that housing is unaffordable for many. She also made a pro-small business pitch.

When Trump's turn came, he appeared more at ease with a relaxed vocal delivery and a measure of control not usually associated with him.

He immediately went on the attack, pointing out that Americans are feeling economic pain, that borders are too porous.

There were no knockout blows

As the debate went on, each candidate had moments of weakness. Trump, predictably, peddled numerous falsehoods. The one most likely to have damaged him — by making him look nutty — was a conspiracy theory rant about immigrants in Ohio stealing and eating people's pets. Harris responded when he finished by laughing incredulously. "Talk about extreme," she said.

Trump's other weak moments were on abortion, where his position has shifted all over the map, and on the January 6 Capitol riots. He dodged two questions about whether he regretted any of his conduct at the time. He lost discipline about halfway through the debate when Harris needled him about bored audiences at his rallies and his family inheritance, but returned to his core message in his final address: that Harris is offering more of the same that Americans have had during the past four years and that the country is on a path to ruin.

As for Harris, she also had a weak moment on abortion where she ducked a question on whether she supports last trimester terminations although on that subject generally, she was far more assertive and confident than Trump.

Her key problem was that she didn't really land any strong or notable takeaway lines. There was certainly no knockout blow. If you came into the debate wondering who Kamala Harris was or what she stands for, or how a Harris administration would differ to a Biden administration, you would have left still wondering to a significant degree.

For example, on the Middle East: "We will work around the clock."

On the economy: "I am offering what I describe as an opportunity economy."

Both candidates made reasonable cases for why they are the strongest option on national security: Harris, on the grounds Trump is easily manipulated by world leaders who flatter and cajole him; Trump by noting the wars in Ukraine and Gaza did not start on his watch and that he ran a tighter ship on border security.

The policy area that matters most

As well as what the candidates said, their body language was important. ABC America's feed ran the two candidates in a split screen for almost the entire time so you could see each one's reaction to what the other was saying.

Harris clearly had a plan to frequently react to Trump as if he were laughable, baffling and weird — messaging the Democrats have been working hard to land. Trump said things that at times warranted that response. At other moments it's possible her non-verbal cues may have jarred voters watching at home.

For example, when Trump said in his opening remarks that "things cost more than they did", Harris shook her head. That could be alienating for viewers who were nodding, and agreeing that yes, groceries and petrol cost more. Similarly, she would look bemused when Trump made remarks such as "the country is in decline" or being "destroyed". Polls repeatedly show many Americans agree with that sentiment and are very concerned about the United States' trajectory.

The policy area of most importance to voters is the US economy and cost of living. Polls show Trump with a 13-point advantage on that issue, so it was important that Harris tried to make up some ground with a resonant and clear message. There will plenty of Monday morning quarterbacking about whether she did so effectively.

Worryingly for Harris, a New York Times-Siena poll released this week showed that 28 per cent of likely voters said they felt they needed to know more about her, whereas for Trump that figure was only 9 per cent.

It's another reason why the stakes were higher for Harris than Trump. Trump never referred to Harris by name, instead calling the Democrat "she" and "her". Some commentators will reach for misogyny as an explanation, but it's also strategic: when Harris is so much less familiar to people than Trump, why give her a hand by reminding voters of her name?