The President in Republican red; former vice-president Joe Biden in Democratic blue. No cross-dressing. Total war imminent.

Friday's encounter was not a game changer. Trump was much more constrained. In a week when he walked out on 60 Minutes, the highest-rated prime time television program in America, and called Dr Anthony Fauci, the country's most respected medical authority, an "idiot", Trump finally listened to some wise counsel from the bowels of the White House who had the courage to speak up. Far less rude and disruptive, Trump was measured and kept to his messages. He was able to land blows that show why he is so locked in with his base.

But Joe Biden was a clear alternative president. He did fine across the issues, especially on getting control over the virus and surprisingly, immigration - an issue Trump believes he owns. Biden countered the Trump attacks on his integrity and ethics that Trump supporters can't get enough of, by simply speaking the truth, and not doing what Trump loves to do - dodge and evade tough questions about how he runs his life, from his business to his taxes to his encounters with women. So Biden more than held his supporters, whose highest priority is simply to get Trump out.

But did Trump, avoiding fatal self-harm, help himself? Were expectations of Trump so low - that he would be so bullying, so abusive, so enraged - that he easily exceeded them and had a good night that kept his prospects for re-election very much alive?

In their debate over COVID-19, the bottom line for voters comes down to: Who do you trust to deal with this? Biden said: "Learning to live with it? Come on. We're dying with it." Trump did nothing to buttress his credibility on managing the pandemic - even though he himself contracted it - and could articulate no plan for capping the spread of the virus rolling out a safe and effective vaccine.

A deeper theme is Trump's inability to see others - especially elected officials - as anything but Republicans or Democrats. Here Biden spoke bluntly. Nearly 70 per cent of Americans believe the country is on the wrong track - a very high number. A significant chunk of that sentiment is the chaos and divisiveness that has been inherent in Trump throughout his presidency. Many are tired of the pitting of one half of America against the other, of the politicisation of everything from the media you watch to wearing a mask in public.

This is where Biden hit home: "I'm running as a Democrat but I'm running to be the American president - not red states or blue states - but the United States ... When I am president, I will represent all of you whether you voted for me or against me. I will say, I'm an American President ... and I'm going to make sure that you're represented. I'm going to give you hope." It works.

Trump has deeply exploited immigration issues from the day he announced his candidacy for president in 2015. And it was on this issue, that pits nativism against law and compassion, where Joe Biden cut through: that it is un-American, against decency, to separate children from their parents when asylum from tyranny is sought in the United States. "Their kids were ripped from their arms and separated. And now they cannot find over 500 sets of those parents, and those kids are alone. Nowhere to go. It's criminal. And violates every notion of who we are as a nation."

On the parallel issue of race in America Trump refused to acknowledge his inciteful language when addressing race. Which provoked Biden to say: "He puts fuel on every racist fire. This guy has a dog whistle as big as a foghorn."

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Trump is highly effective as the outsider, the disrupter, the guy who barges into Washington and kicks over the furniture, who calls out the elitism that deprives working Americans of what they deserve. So when Trump can snap at Biden that, given his decades in the Senate and his time as vice-president, "you had eight years to get it done, now you're saying you're going to get it done because you're all talk and no action Joe," it has deep bite.

Did this final debate give Trump a boost? We will know if we see a tightening in the polls in the next few days. Specifically, if we see a Trump recovery in the crucial swing state of Pennsylvania, as significant parts of the debate had to do with jobs and energy there. And if we see a resurgence of Trump in conservative states that are in danger of slipping away, such as Georgia.

As I have previously written, presidents lose re-election when it is clear to voters that they cannot manage the crises that are engulfing them. For Jimmy Carter in 1980, it was the humiliation of the Iran hostage crisis, an oil embargo, and a terrible recession. George H. W. Bush, exceptional manager of the end of the Cold War and hero of the first Gulf War, could not conquer a brutal recession.

Trump faces that very issue in this pandemic election, where COVID-19 has proved immensely bigger and more lethally effective than he is. That, and an approval rating of well under 50 per cent - a benchmark every successful president seeking re-election since the 1940s has vaulted - remain the principal drivers of this election.

If Trump is to relive the winning rally he enjoyed against Hillary in the final days of October 2016, that comeback has to begin now.