Labor is banking on a fresh pitch over energy prices and hospitals to win over voters in key seats ahead of a Super Saturday of by-elections.
Opposition Leader Bill Shorten acknowledged the Queensland seat of Longman would be the toughest of the five fights, as he launched the campaign for Labor candidate Susan Lamb, whose resignation over dual citizenship triggered the poll.
"It's not how you start, it's how you finish," Mr Shorten declared, having taken part in a local fun run on Sunday.
The federal opposition's latest pledge to voters is spending $1.4 billion over five years to keep in place the energy supplement for pensioners and welfare recipients.
Draft laws to scrap the energy supplement for anyone who has become a new pension- or allowance-recipient since September 20, 2016, are currently before the federal parliament.
Axing the energy supplement will mean a cut of $14.10 per fortnight to single pensioners, or around $365 a year, and a cut of $21.20 a fortnight, or around $550 a year, to couple pensioners.
Labor has also been hammering the message of health spending, with Mr Shorten telling the party faithful in Longman, "Send Susan Lamb back to Canberra with a message from Queenslanders: 'Money for hospitals, not money for the banks'."
Prime Minister Malcolm Turnbull told reporters in Townsville the federal opposition leader had made an admission of failure with his energy supplement policy.
Mr Turnbull said it was better to introduce policies to bring power prices down than keep people on the carbon tax compensation.
"He's admitting he's failed before he's even started. He is a quitter," Mr Turnbull said.
The Liberal National Party is ahead in Longman 51-49, according to the latest ReachTEL poll.
But Labor strategists believe the result is so tight the winner may not be known on Saturday night.
A poll taken in Tasmania's Braddon late last week put Labor on 52 per cent of the two-party vote, with about two-thirds of voters expected to preference the opposition over the government.
Liberal senator Eric Abetz said a government win in Braddon, or any of the other seats, would be a "history-making occasion".
The Liberals are not standing candidates in Perth and Fremantle.
The Centre Alliance's Rebeckha Sharkie is strongly tipped to retain her South Australian seat of Mayo against a challenge by the Liberals' Georgina Downer.
Labor's Brendan O'Connor talked down the leadership impact of any losses.
"Bill Shorten will be leader at the next federal election," he told Sky News.
Liberal frontbencher Josh Frydenberg dismissed any pressure on Mr Turnbull, given no government has won an opposition seat in a by-election for 100 years.
"The reality is we are trying to climb Everest in winning these by-elections."
