In a nutshell

Scott Morrison stayed south, while Bill Shorten went north, with the two leaders keen to improve their standing in their respective weak spots. Morrison was campaigning in South Australia, where the government is trying to hang on to the marginal seat of Boothby and wrest back Mayo from independent Rebekha Sharkie, while Shorten was campaigning in the crucial Queensland marginals of Herbert, Flynn and Dawson.

After attempting to ride out the political controversy surrounding an $80m water buyback overseen by Barnaby Joyce when agriculture minister, the Coalition sought to draw a line on the issue by announcing the auditor general would look at commonwealth water purchases over the past decade. Labor is pushing for a judicial inquiry into the buybacks, and is unlikely to let the issue rest.

Attention turned to preference deals that will be determined in coming days after new polling showed Clive Palmer’s multimillion-dollar advertising blitz was paying off. If anyone was in any doubt that his United Australia party could buy its way into parliament with an estimated $30m advertising spend so far, a Newspoll of four crucial seats has found his party has won back support among voters, including in the Townsville centred seat of Herbert, where his support is as high as 14%. This is despite Palmer leaving workers unpaid when Queensland Nickel collapsed in 2016 with debts of $300m.

With the massive caveat that these marginal seat polls have a high margin of error of between 3.9% and 4.3%, the numbers are still pretty extraordinary and show Palmer could well be a kingmaker on 18 May. He is also well placed to snare a Senate seat.

Labor and the Liberals are in talks with Palmer about potential preference deals that could prove decisive, and this will be a crucial space to watch in coming days. Guardian Australia’s Amy Remeikis reports that Palmer’s candidate in Herbert has already warned that he would quit the party if Palmer did a deal to preference Labor.

Elsewhere on the trail

John Howard was in the New South Wales seat of Reid, held by outgoing Liberal MP Craig Laundy, pressing the flesh with the party’s candidate, Fiona Martin. Howard bumped into the Labor party’s Sam Crosby, who has been campaigning for many months, and also had an awkward exchange with reporters about his support for Martin. The former PM said the Liberal party had found “a really outstanding candidate” in Martin, but he later conceded he had only just met her.

“No I hadn’t met her before, no. No, I literally hadn’t, but so what? I had heard about her, I heard that she had grown up in the electorate and attended Santa Sabina school in Strathfield, which I know of quite well, but look there’s nothing strange about that.”

Picture of the day

Facebook Twitter Pinterest Scott Morrison heads a soccer ball at Manson Park in Bellevue Heights near Adelaide. Photograph: Mick Tsikas/AAP

As AAP reporter Alex Druce quipped, this is an incredible photo of a concussion playing out in real time.

Required reading

Rather than required reading today, required listening has to be the trainwreck radio interview between Barnaby Joyce and ABC’s Patricia Karvelas on radio national last night. The former agriculture minister was attempting to defend his handling of the water buybacks he oversaw in 2017, but the performance required damage control from the government on Tuesday morning. You won’t believe your ears. The highlights can be heard here.

Tweet of the day

AEC (@AusElectoralCom) A record 96.8% of eligible Australians are enrolled for the 2019 federal election. This is the most complete electoral roll in history with youth enrolment also an all-time high of 88.8% (18-24 YOs) #ausvotes pic.twitter.com/CjIK5Dl5gX

In good news for democracy, the Australian Electoral Commission has revealed that with the close of enrolments almost 97% of Australians have registered to vote at the forthcoming poll – a record high. Youth enrolments are also up, boosted by the need to enrol to vote for the 2017 same-sex marriage plebiscite.

What’s next?

Shorten remains in Queensland campaigning in Herbert, with the focus still on wages, while Morrison has left South Australia and is heading to Darwin.