THE Perth studio audience of undecided voters gave the campaign’s first debate to Bill Shorten by a decisive margin.

Of the 48 present, 25 thought the opposition leader won, 12 believed the night was Morrison’s and the rest were undecided.

In my opinion, the outcome was less clear cut. I’d score it pretty evenly. Shorten had more to say. Morrison had more energy.

At one level the Seven West Media debate was an unsatisfying encounter, perhaps because we’d heard almost all of it before. But nevertheless it was revealing because, despite forced grins, the strain and effort were so visible in this “best in show” hour.

Perched uncomfortably on their stools, with questions coming from two journalists and audience members, both leaders had tried to prep to the nth degree, although Shorten had a couple of lapses.

There were a few spontaneous comebacks – debating is part of a politician’s skill set, though perhaps not as well-developed as once – and the audience managed a handful of laughs.

The exchanges did lay out the essence of how these two leaders are fighting this campaign.

Shorten has the detailed policy, with big initiatives that will appeal to voters. But his program is costly, and he has to mount a heavy argument to support the tax changes that will pay for it all. He describes these as closing loopholes; Morrison casts them as massive increases.

Morrison is running hard on lines that boil down to stick-with-what-you-know, and you-can’t-trust-Bill. In the campaign he is all attack and that, and a certain quickness, came through repeatedly in the debate.

The contrast in messaging was summed up at the end. “He’s not telling you what the cost of change is,” Morrison said – in other words, don’t venture down the scary Shorten road.

Shorten’s riposte was to point to “the cost of not changing” – in other words, voters would be worse off – in everything from hospital care to climate change – unless they took the new path he offered.

Shorten was caught out when asked the price of a popular electric car.

This was the modern version of that old question to leaders about the price of milk and bread.

“I haven’t bought a new car in a while so I couldn’t tell you,” he admitted.

Like the cocky kid in the class, Morrison jumped in to say: “I can tell you how much [an] electric car costs, more than [a] standard – it’s $28,000 […] that’s for the same type of car”.

That gave Shorten the opportunity for a quip to cover his inability to answer what someone who is advocating an ambitious target for new electric cars should have known.

“Well that’s great, we’ve got a Prime Minister spending his times in the motor pages” he said.

Morrison quickly came back: “Well that’s where most Australians often spend their time, mate […] they read about cars, they read about footy, they read about the races […] ”

Shorten provided a robust defence of Labor’s policy to cancel cash refunds from franking credits, but Morrison forced him to concede on a detail.

Pressed on the cost of Labor’s emissions reduction policy Shorten said there wasn’t “one number”, but was strong on the need for action. Morrison didn’t get far on trying to raise the alarm on border security.

Asked about the awkward subject of Clive Palmer and preferences, Morrison abandoned his earlier line of leaving Palmer to speak for himself, saying: “Clive Palmer should pay his workers and Clive Palmer should settle things up. […]

“Clive Palmer should do what every other Australian should do and that is they should abide by the law […] But “do we think that the United Australia Party would be more dangerous to the Australian economy than Bill Shorten, the Labor Party and the Greens? Well I’m sorry, I think Bill Shorten, the Labor Party and the Greens are”.

Shorten drove home the point that Palmer owed $70 million to the taxpayers, asked rhetorically how Morrison and his government had been taken hostage by Palmer and Pauline Hanson, and conjured up the spectre of Palmer calling in a debt from the government.

Each leader stepped carefully when pressed on what they admired about the other.

The true answer probably is “bugger all”, but that’s not an acceptable one.

Morrison came closest to it however, saying: “I respect anyone who serves in the Australian Parliament”.

Shorten produced unexpected praise for what Morrison was doing on mental health and for being “a man of deep conviction”.

When asked why voters should trust them to do what they promised, and what they would do to restore trust, both sounded lame.

Morrison pointed to party rule changes to protect prime ministers and then defaulted to “who do you trust” on economy, immigration etc.

Shorten referenced Labor’s plan for an anti-corruption commission, and said Labor had put all its policies out for people to see.

But on trust, neither had a fundamental answer to what is at present the unanswerable question in Australian politics.

Michelle Grattan is a professorial fellow at the University of Canberra. This article was originally published on The Conversation.