Trump will seal the deal with nonstop playing of the race card and the sex card. He believes that just as America had had enough of eight years of Barack Obama before granting him the presidency, that in 2024 the country is not viscerally ready for a black female president. Trump knows that his voters do not want or respect Kamala Harris, that she makes his base uneasy, and he knows they want to vote for him to evict her from the White House.

How does Harris win from here?

The ground game is everything for Harris. Trump has a ceiling of 45-47 per cent of the popular vote. Harris must keep him there. What is particularly daunting is that almost all the polls in 2016 and 2020 undercounted the Trump vote by two to three points nationally. In 2020, Trump won 46.9 per cent of the popular vote; the poll averages had him at 44 per cent. Biden won enough – 51 per cent of the vote – to beat him.

But Harris is still short. While she’s winning back the Democratic voters who gave up on Biden, she still trails the support Biden had in 2020 from under-30 voters by 12 percentage points. She is still 10 points under Biden’s support from black voters, six points under Biden with Latino voters, four points under Biden with men, and – still – two points under Biden with female voters. Harris’ trajectory is on course, but she has not yet locked in those votes.

This debate will help her do that.

Harris is also targeting more voters who are not committed to Trump, especially women on abortion rights. For women under 45, abortion rights – not the economy – is their No.1 issue. Harris wants to garner some of the 15 per cent of Republicans who did not vote for Trump in the primaries. The endorsements from staunch conservative Republicans Liz Cheney and her father, former vice president Dick Cheney, will help.

Harris reached those voters in this debate and gave them reasons to break with Trump.

Harris is carpet bombing her campaign with the jet fuel of politics: money. She raised US$361 million in August (US$230 million more than Trump). She has US$110 million more in cash on hand. This means she can fund the field offices and armies of volunteers in the suburbs and exurbs of Republican states to cut Trump’s margin, if not beat him outright. If Harris carries Pennsylvania and Georgia, she is all but assured of victory.

Trump saved his best – his most effective remarks – for last: that Harris has had three and a half years to do all the things she talked about, “but you haven’t done it”.

It’s a great argument. But it was too late to recover from what will go down as a genuinely shocking performance.

And Taylor Swift agrees.

Bruce Wolpe is a senior fellow at the University of Sydney’s United States Studies Centre. He has served on the Democratic staff in the US Congress and as chief of staff to former prime minister Julia Gillard.