Grant Robertson says it is a "Rebuild Budget"; Simon Bridges says it is a "Tax and spend, borrow and hope" Budget. But both would they say that, would they not?

In reality, this Budget is neither as positive as the Minister has painted it, nor as negative as the Opposition claims. It looks to be a cautious and fiscally prudent document, which maintains but does not accelerate significantly the new expenditure track of the previous Government in health and education; allows through reprioritisation of existing spending the introduction of some of the Coalition Government's new programmes; and reduces the overall level of debt to below 20%.

Where the Budget has not been able to deliver expected policies - like the $10 per visit reduction in the cost of going to the Doctor - it makes it clear that the policy will be achieved over the balance of the Government's term. While conservative, given the overall fiscal position, the staging of commitments is a good step forward, especially since too often in the past commitments shelved one year by successive Labour and National Governments have often disappeared altogether.

Despite the Opposition's concern about more borrowing, the real questions over this Budget arise not from its economics - the Minister has made a good fist of balancing the numbers and projecting surpluses into the future - but with the politics.

While Mr Robertson wins plaudits for making clear what was not done in this Budget will be done in the next before the 2020 election, he has at the same time tied himself firmly into a straightjacket. He now has no alternative but to honour those commitments. While many will welcome that, there are some potential negatives.

First, his straightjacket means that, in implementing these commitments, he has left himself little to no headroom for anything that might emerge in the future. Put simply, Labour has played all its big cards in its first year - today - and the next two Budgets will be about implementing the details. Knowing the Government's hand this early leaves the Opposition plenty of scope to develop attractive alternative policies over the next two years. And it makes life a little more awkward for New Zealand First and the Greens. Their trophies are now pretty much in the cupboard, leaving them with the perennial support party problem of relevance between now and the next election. And Labour needs both of them to make it over the electoral line in 2020 to remain the Government.

Second, there is a heavy reliance on the domestic and international economies continuing to perform well over the next two years. Even the notoriously and inveterately overly optimistic Treasury forecasts show there is little headroom should things falter on the home front, let alone there be an international (erratic America-first Trump-induced?) economic correction before 2020. In that event, the Government could be left high and dry with a less than half completed programme and no good news to show in its election-year Budget.

And then there is the reaction of the traditional Labour leaning groups like the teachers and the nurses. It is clear that the significant pay increases they were expecting as their payback for loyal support over the years are not among the new education and health spending in the Budget. Already both are making noises about this. So will the nursing and teaching unions rest quietly, and settle for jam tomorrow, in potentially uncertain times, or will they demand their slice of the pie now? According to their own narrative, they were held back so much during the nine years of the National-led Government, so they seem unlikely to be quiet now "their" party is in power.

This essentially stand-pat Budget certainly passes the good management and solid accounting tests, and the Government will be clearly (if vainly) hoping that, in the absence of any coherent economic growth strategy, this "reliable hand on the tiller" approach will assuage some of the concerns of the business community and stem the erosion of confidence. It probably will not do that, because the leading business and employer groups have now become just as stridently partisan as the unions they criticise. The Government will calculate that business has therefore painted itself into a corner, so probably will not be too bothered by the criticisms.

Of more concern will be the fear that the Budget may fail to satisfy the many who voted Labour last year believing the new Government would do all the things it promised in an immediate new wave of Savage-like compassion and commitment. If they feel that instead they have ended up getting a Budget pretty much the same as they could have expected from National, Labour has a problem.

Grant Robertson says this Budget is but the foretaste of what is to come in 2019 and 2020. Given that and the unreal expectations he and his colleagues let build up for this Budget, he could be dangerously tempting fate for the next two!

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