"Since then of course his popularity has waned, his net satisfaction rating is now negative, it is 50-50 I guess in the polls … I think it's a close contest. I think (Labor leader Bill) Shorten is a person who runs on confidence, he's had a bit of a boost to his confidence in recent days so he's looking slightly better while Turnbull's been struggling."

John Hewson says there are too many vested interests. Credit:ABC Q&A

Commenting on Mr Turnbull's decision to frame the election around the Senate's rejection of a bill to bring back the Australian Building and Construction Commission, Mr Hewson said: "I'm not sure you can sustain that … for an entire campaign. I think other issues will come to the fore. They tend to go back to issues of education and health. Important issues."

Mr Hewson said the prime minister's popularity had taken a hit in part because he has disappointed his more progressive supporters and had compromised with right-wing Liberals to get the top job.

"Look, obviously Malcolm did a deal to get there and the deal he did actually compromised some of the basic positions that he'd previously held and held publicly. There's a fellow running in the seat of Wentworth, my old seat, against Malcolm, who just wants the old Malcolm to come back. The guy that stood for gay marriage … and climate change and tax reform and so on. And I think that's been a major reason why his popularity has collapsed."