Voters are seeing the first indications of deals between major and minor parties as the ballot boxes open for early voting ahead of the federal election.

Scott Morrison and Bill Shorten are both in Perth before going head-to-head in a debate for the first time.

The leaders will meet as a new poll shows the gap between their parties has narrowed in the past fortnight.

The Australian’s Newspoll shows Labor still leading the two-party preferred vote with 51 per cent to the coalition’s 49 per cent, but it’s the best result for the government since Mr Morrison became prime minister in late August.

Opposition frontbencher Penny Wong said Labor knew the polls would tighten in the final weeks of the campaign.

“We always anticipated this election would be tight,” she told ABC Radio National.

“We always anticipated we’d see a dirty campaign from the Liberals and we have. We always anticipated it was going to be tough. I mean, Labor has won from opposition three times since World War II.”

Deputy Prime Minister Michael McCormack said he was hearing from people they were worried about “shifty Bill Shorten”.

“The fact is, if you look at polling, no matter who it’s done by, (it) doesn’t always accurately reflect the sentiment of voters,” he told reporters in Cairns.

“A week is a long time in politics. A day can be a long time in politics. The fact is May 18 is the date when they will count all of the votes.”

The poll showed drops in the primary vote for both parties – the coalition down to 38 per cent and Labor falling to 37 per cent – making preferences from minor parties important.

Early voting opened on Monday, and how-to-vote cards being handed out around the country showed what preference deals had been made.

Despite labelling Clive Palmer a “tosser” and “con man” in recent days, Labor has put the mining magnate second on its how-to-vote cards in Tasmania.

The opposition is preferencing his United Australia Party second in Franklin, held by Labor MP Julie Collins, and also in independent MP Andrew Wilkie’s neighbouring seat of Clark.

For its part, the Morrison government has described Mr Palmer as the “least worst” alternative option, after striking a preference deal with the billionaire in South Australia.

Pauline Hanson has thrown Mr Morrison a political lifeline by putting Labor last on One Nation how-to-vote cards in four critical seats – frontbencher Peter Dutton’s Queensland seat of Dickson, the WA seats of Attorney-General Christian Porter and Andrew Hastie, and Petrie in SA for Luke Howarth.

The debate on Monday night will be hosted by The West Australian and air on 7TWO at 7pm AEST.

Voter concerns around tax and climate policy are expected to dominate.

Mr Morrison has told Nova radio in Perth that he plans to be himself and be up-front with people.