Like every budget, Tuesday's will be a combination of measures and arguments, each with political and economic dimensions and motivations. Distinguishing the politics from the economics will be the hard part.
It promises to be a budget in which the government does a lot of crying poor. That's partly because Malcolm Turnbull is likely to call an election within a week of the budget, but is prevented mainly for political reasons from making many big spending promises.
Politically, this government made so much fuss about debt and deficit while on its way to power that, though it's made little progress in reducing the budget deficit and halting the growth in debt, it dare not be seen consciously adding to it.
Economically, returning to surplus isn't urgent, and increased borrowing for worthwhile infrastructure would make much sense.
As part of the crying poor, when state politicians hit the feds for more money, federal ministers reply that they can't help because, though the states are running surpluses, the Commonwealth is still in deficit.
Don't believe it. When the states say they're in surplus, they're referring to their "operating" balance, which is their revenue less their recurrent spending. When the feds say they're in deficit, they're subtracting from revenue not just their recurrent spending, but also their infrastructure spending.
Add the states' infrastructure spending to their operating surpluses and you find that – measuring it the way the feds do – they're still in heavy deficit. (Which is as it should be. If anything, they should be investing more.)
Or, to put it a better way, by insisting on their antiquated practice of including capital spending in their measure of the deficit, the feds are exaggerating the size of their deficit problem.
This financial year's budget papers forecast a deficit of $35 billion (since revised to $37 billion), which included capital spending of about $21 billion.
Further capital spending of $17 billion (including on the National Broadband Network) is hidden in the "headline" deficit, meaning capital spending accounted for 8 per cent of headline spending. Last year it was 9 per cent.
Another thing we'll hear a lot of on Tuesday night is that the government is "living beyond its means" and must mend its ways and live within its means, just as households do.
This is nonsense. It's Scott Morrison doing his best Joe Hockey impression. If you measure them the way Morrison does for the government – that is, by including borrowing for investment in with day-to-day expenses – our households are living way beyond their means.
Indeed, Australia's households have one of the highest debt ratios in the developed world.
Do you think it's a crazy, irresponsible thing for so many households to borrow many multiples of their annual income to buy the home they live in?
Of course not. For most it makes lots of sense. Is a government – state or federal – that borrows to build public infrastructure that will serve the community for decades, adding to our productivity, living beyond its means? Of course not.
National governments may be said to be living beyond their means when their recurrent spending exceeds their revenue, but even that is too simplistic.
Why? Because governments aren't the same as households and it's ignorant to pretend they are. Governments have responsibilities households don't have and also have powers households don't have – such as the ability to impose taxes and even, for national governments, to print money.
One highly relevant government responsibility is to help limit economic slowdowns by running operating deficits – by allowing their recurrent spending to exceed their revenue – while spending by the private sector is weak.
Does that sound too Keynesian for a Coalition government? Too Keynesian for Turnbull who, while opposition leader in 2008, vigorously attacked Kevin Rudd's fiscal stimulus?
Don't believe it. It's clear we'll hear a lot of the argument that Turnbull and Morrison can't cut government spending much at present because the economy is "in transition" and so not yet growing strongly.
That's a Keynesian argument, the antithesis of an austerity policy – though both men would die before uttering the K-word. And it's a sound argument – which is why we've been hearing it since Labor was in power. It was just excuse-making then, but it's true now, apparently.
Of course, it's also true that no politician wants to cut spending just weeks before an election.
Economically, there's no problem with continuing recurrent budget deficits. A better question to ask on Tuesday night is whether the spending that makes up the deficit is going on good programs or poor ones.
