Speaking to the Observer this weekend ahead of her first Budget as Chancellor, Rachel Reeves said that she would have to better her predecessors by delivering a hat trick: 1945-style rebuilding of the country; 1964-style modernisation of the economy; and 1997-style turn-around of the public sector. Her goal is nothing less than matching the “greatest economic moments in Labour history”.

We need to set that scale of transformative ambition against the very real constraints facing the Chancellor, as she takes to the despatch box on Wednesday. She will be bound by concern about financial market responses (after credit agencies downgraded French sovereign debt last week due to a rising deficit and anxiety about political will); Labour’s manifesto pledges; and the political costs of driving through difficult reforms.

Given her difficult balancing act, this will not be a Budget of giveaways. But it will be a hugely important statement of intent. This is what the team at the Centre for Progressive Policy (CPP) will be looking for from the Budget:

1. The why: successfully delivering the Budget will mean making hard choices. How the Chancellor frames those choices - what she prioritises, and why - will give us a clearer benchmark to assess the government’s agenda and values.
2. The how: the government also has to decide on its preferred partners-in-power, and its financial strategy, as it works to meet its goals. The machinery of government – especially finance and the fiscal rules, and how Whitehall and the nations and regions coordinate – will determine whether the UK makes progress on growth and reform over the parliament.
3. The what: the Chancellor will want to set out a few emblematic policies now, ahead of next year’s Spending Review, to bring the “how” and “why” to life. Some of these will be driven by the need to respond to ongoing crises or the planned roll-out of certain policies. We will be looking for chances to turn challenges – in local government, childcare, or elsewhere – into opportunities to deliver both growth and inclusion.

Our first test, then, is whether we have a clearer sense of the government’s priorities after Wednesday. Will the Chancellor capture and articulate the story of (at least) the first half of this parliament?

Today, the Prime Minister is warning of “the harsh light of fiscal reality”; while yesterday the Chancellor was bullishly talking about “rebuilding our country and seiz[ing] the massive opportunities”. Both can be true at the same time, but the government has a choice over which it emphasises. What does Reeves say when she declares “this is a Budget for X” in her first minute?

That question goes beyond the craft of speechmaking. It will help us see, for the first time with the machinery of Whitehall behind her, how the Chancellor’s rhetoric is evolving as the challenges of government become clear. How are the five missions (growth, health, energy, security, opportunity) reconciled with Reeves’ Mais lecture vision of a “broad-based, inclusive and resilient economy”? In this month’s modern Industrial Strategy, the commitment to “long-term, sustainable, inclusive and resilient growth” is made six times – but how will government approach the trade-offs between those different goals?

Chancellors and Prime Ministers in the past have bemoaned “pulling the levers” of government, before slowly realising that nothing happens because either the wires have been cut or the lever was never connected to anything.

Local government is facing widespread financial crisis. The NHS is consumed by meeting urgent short-term goals around clearing waiting lists. Universities face a funding squeeze even as they formed the basis of “Investment Zones” for growth over the last few years. Businesses face potential tax rises when they’re also being asked to raise investment. To bring any of those partners along with her, the Chancellor will need a compelling narrative of what a new compact, a new way of working, could look like.

In our report last year, Funding Fair Growth, we made the case for raising investment through a revised fiscal rule, while tying additional investment to public service reform. Through the work of our Inclusive Growth Network, we have championed the role of local and sub-regional governance in responding to local conditions and pioneering innovative policy responses – something government can amplify by decentralising and devolving by default. And our work on regional inequalities has shown that business communities across the UK can be brought into a growth plan which backs clusters of excellence in all sectors and communities. Who will the government put at the front of the queue for partnership, and will the offer be attractive enough for them to say yes?

Nearly four months into the new parliament, much ink has been spilled running the rule over dozens of potential tax rises or spending cuts. We won’t relitigate that work here.

At CPP we will be looking out for how the government develops its position on a few specific manifesto commitments. These are the “no regrets” investments, which could both raise our economic growth rates, and concentrate benefits on those who are worse off:

• Childcare (making sure the quality and availability of services keeps up with the expansion of free hours);

• Population Health (addressing the underlying causes of ill health in our economy);

• Devolution and local government (by helping manage a shift towards prevention in public service delivery); and

• Social capital (investing in the sources of trust, resilience and growth in all communities).

Ultimately it will be for the Spending Review next year to settle the details across all policy areas. The important thing for Wednesday is that the policies the Chancellor mentions (or avoids) provide the proof-points for the wider story she is trying to tell. Individual policies should illuminate, rather than obscure, the Chancellor’s wider canvas.

Rachel Reeves has already set herself an audacious set of goals for the Budget, reflecting the ambition of the Mais lecture and the rhetoric of a decade of renewal.

The Budget will write the next chapter of the government’s economic story. In the crucible of hard economic choices, we will get a clearer sense of the underlying values and narrative of this parliament. We will understand how the world outside of Whitehall fits in with goals. And we will have a few iconic set-piece policies to point to, helping us move from vision to reality.