Andrew Adonis, the head of Labour's growth review and the architect of the project, has warned that cancelling the programme would be an "act of national self-mutilation".
Osborne's instinct will be to use the extra revenue for faster deficit reduction or tax cuts. But Labour can argue for an alternative centred around investment.
Osborne is determined to claim that there is a "black hole" in Labour's spending plans, whatever the Office for Budget Responsibility may say.
Asked to choose between a third runway at Heathrow and High Speed 2, Balls replies: "third runway". Miliband would say the reverse.
The opposition should worry less about the growth rate and more about developing its own story about the economy.
With the return of the economy to growth, the shadow chancellor seeks to shift the terms of the debate in Labour's favour.
Unlike the Conservatives, a Labour government would make sustainable energy a major national priority and give business the confidence to invest.
Balls signals that he is willing to support the Chancellor's new curbs on claimants, including a seven-day wait for benefits.
The Chancellor's decision to set out plans for 2015-16 nearly two years in advance has everything to do with politics and nothing to do with economics.
By repeatedly criticising the Chancellor for missing his deficit targets, the party risks reinforcing the impression that borrowing is always an economic ill.