The answer is simple, which is why we can't see it. The economic model is broken.

Until recently there were just three requirements for political success.

The first rule was to understand who you need to appeal to - not just to come to power but also to remain in office. Truss stumbled at the first hurdle. She knew the ageing members of the Tory party would get her over the threshold of No.10. These are the sort of people she'd listened to for years over tea and biscuits, telling her what was wrong with the country, why Britain had stopped being Great, and how things needed to change. Truss drank (approximately) 14,952 cups of tea (at say, two per day for 21 years) nodding along with, agreeing with, and appealing to, these voters, the ones who would deliver her victory in the party ballot. Unfortunately for her, these are exactly the people you don't want to listen to once you reach high office.

Party members are, by definition, unrepresentative. The people who elected Truss were older; wearing twin sets and pearls or cardigans and tweed. Sure, she needed their endorsement to become leader, but she didn't realise that was the moment she needed to stop listening to them and, instead, adopt sensible policies. But she'd become brainwashed, a zombie leader. Thinking she could fashion the world the way she wanted it through sheer willpower, she thought she could ignore those she really needed to keep on side if she wanted to remain in power: the markets.

They dismissed her dogma, punctured her posturing, and walked on by, ignoring the flailing woman in her blue dress, struggling to make herself heard from the hard brick pavement of Downing Street. Truss forgot who she needed to keep on side if she wanted to stay PM. No politician lasts very long once they begin listening to voices emerging from inside their head.

The second rule successful politicians instinctively understand is how to place themselves at the centre of government and seize control of the agenda. This was where Malcolm Turnbull failed. Despite overwhelming support after taking over from Tony Abbott he vacillated, canvassing different ways forward and discussing ideas. Instead of immediately calling an election to establish his agenda the tiller pushed first one way, then the other. He squandered early enthusiasm as he seemed uncertain of where he was taking the country. Turnbull only just scraped back at the election and the rest is history. No prime minister can ever survive the sharpened daggers of their own colleagues once there's blood in the water and the smell of weakness floating through the corridors.

So if the first rule is 'who': awareness of the people you need to support you if you wish to remain in power. And the second is 'how': timing and implementing control. The third is 'what'? Policy. This is the democrat's economic handbook, laying out how they'll lead the country into the future. It also explains why democratic politicians the world over are currently in such difficulty. The guidebooks of the past are not just no longer relevant, they're wrong.

We still act as if we inhabit a world where economic growth is not simply desirable, but attainable. A world of infinite resources. One where urgent or critical environmental challenges (such as floods, and warming; shortages of food and minerals) will suddenly disappear. These require new answers. Unfortunately the only solution that political handbooks offer is, "infrastructure".

While anyone who becomes prime minister inherits a massive bureaucratic apparatus to convert policy into practice, it's an organisation without direction of momentum. Converting this massive superstructure into something that can deliver practical outcomes has eluded politicians for years. It's because the model underpinning the economy - that we're one country, with everyone sharing in that prosperity - has finally snapped. This is the key to understanding the present crisis of democracy.

Much of Italy's early political instability can be traced back to regional divisions between a growing north and economically blighted, poverty stricken south. Similar fissures have resulted in demands for Brexit in the UK and the appeal of nationalist parties and demagogues here.

When Australia's polity began fracturing the initial reaction of the major parties was to offer soft bribes to voters, in the form of say, sports programs or public transport services. This isn't enough any more. Voters at the last election abandoned both major parties. While Labor formed government, it did so with the lowest proportion of the vote since 1934. People might not be able to articulate the policies they want, but they know Liberal nor Labor offer viable answers, either.

And this is why so much is riding on Tuesday's budget.

READ MORE NICHOLAS STUART OPINION COLUMNS:

Nobody expects Treasurer Jim Chalmers to deliver an answer to our economic challenges or lay out a path forward. This set-piece does, however, offer him an opportunity to begin establishing a new framework for the future. That's why the key to his speech will be the part that discusses wellbeing. Chalmers needs to drag the conversation away from earlier ways of measuring the economy, like GDP, and shift the focus instead to what we really want from life.

In future there will never be enough money to continue the way we are. We can't support increased spending on defence and aged care, the NDIS and medicare, because the economy isn't growing fast enough. Nor are more migrants the answer: something will have to give. This budget gives Chalmers his chance to rewrite the third rule of politics and get us to focus on what we want.

There's much more to life than growing GDP.