But Mr McGowan says he does support an emissions trading scheme.
A Newspoll commissioned by The Australian newspaper shows voters find Mr McGowan likable and caring but most think Premier Colin Barnett is a better economic manager.
The poll, published on Monday, shows 54 per cent of voters believe Mr Barnett is more capable of handling the state's economy, compared to 33 per cent support for Mr McGowan.
But the leaders are tied at 81 per cent when it comes to having a vision for the state.
Responding to the poll, Mr McGowan said he opposed a carbon tax but was in favour of an emissions trading scheme, and he would support the mining tax only if WA got back the exact share it put in.
"We see Western Australia as being more than just mining, whilst acknowledging the importance of mining," he told News Ltd.
Newspoll has pointed to a landslide election win for the WA Liberals on March 9, putting it ahead of Labor 57 to 43 per cent on a two-party preferred basis.