By ABC's Annabel Crabb

Photo: The first leaders' debate of the election campaign was held Sunday night at the National Press Club. (AAP: Alan Porritt)

Against the tenderly nonpartisan mauve of the National Press Club stage, Mr Rudd and Mr Abbott took turns to deliver mild-mannered declamations of their intent. Both managed to answer the questions put forward, but it was hardly a debate at all, writes Annabel Crabb.

Both participants prepared for the first debate of the election season in their own way.

The Prime Minister spent the morning like Joan of Arc, seeking "divine guidance" at church. The Opposition Leader ran 14 kilometres from Hyde Park to Bondi, handcuffed to another man. Both preparatory regimes appeared to have been successful, in that neither man tripped over, swore, forgot the name of any major public sector agency or addressed host David Speers as "Kerry".

Against the tenderly nonpartisan mauve of the National Press Club stage, Mr Rudd and Mr Abbott took turns to deliver mild-mannered declamations of their intent.

When new questions were asked, each of them invariably found something to say, though not really to each other.

What is a debate, anyway? Last week, Mr Abbott sketched some fairly broad definitional parameters, arguing that when he and Mr Rudd were interviewed one after the other on a radio program, that was a kind of debate.

And this first encounter was definitely the one-interviewed-after-the-other kind.

Mr Rudd opted early in the piece for a three-letter slogan.

Most of his considerable ingenuity was devoted to the task of getting the letters G, S and T involved in as many responses as he could.

Does the GST have anything to do with Mr Rudd's election policy? Not a bit of it. Is Mr Abbott planning to do anything to the GST? No. But Mr Abbott is doggedly refusing to rule out including the GST in his wholesale review of tax policy planned after the election, and to a lean and hungry Prime Minister looking for trees to bark up, that's as much as you need.

There were a few surprises. Mainly for the leaders, who both seemed surprised to be asked about aged care; Tony Abbott wittered on for a bit about reducing paperwork for staff in the aged care system, while Mr Rudd - uncharacteristically missing a chance to warn about an increased rate of GST on Midsomer Murders or Sudoku - responded with an unscripted reverie about the amazing things you could do with computers these days.

Neither, similarly, was expecting to be asked about Sydney Airport, that towering monument to decades of political indecision and fecklessness on a grand and multi-partisan scale.

Mr Abbott - rather recklessly, but then he is an Opposition Leader - promised he would make a decision one way or another in his first term.

Mr Rudd reminded everyone that he was from Queensland. He suggested that the "good folk of Sydney" should remember that theirs was not the only airport in Australia (an entirely undebatable point, though were it otherwise the domestic flight industry would be fairly pointless, thus sorting out the congestion issue).

In any event, he declared, Albo was in the process of sorting it all out.

But the greatest challenge of the debate was its most important question, which came from The Sydney Morning Herald's Peter Hartcher, and concerned the nation's apparent inability to maintain a solid revenue base for all its incremental spending plans. What will you cut, or what taxes will you increase, Hartcher asked.

Mr Abbott declared that he would "grow a healthy economy". Mr Rudd said he would boost productivity - and then added that he was very worried about how crippled families would be by an increased GST.

The hopeless thing is that this question can only be answered by both participants together - if there are large and painful decisions to be made in this country, as seems increasingly obvious, then the only workable way to make them is if all parties put the national interest above their own.

But that would be another kind of debate entirely.

Annabel Crabb will be writing on the election for The Drum regularly throughout the campaign. She is the ABC's chief online political writer. View her full profile here.

Leaders answer questions, but where's the debate? - The Drum (Australian Broadcasting Corporation)