The negotiations with Mr Palmer are expected to lead to a formal announcement on Monday when early voting begins and all parties are expected to intensify their campaigns as Australians cast their ballots.
While support for Mr Palmer’s United Australia Party has collapsed in recent years after a series of controversies, his heavy advertising program has put him back in the political race at the expense of Senator Hanson and her One Nation party.
The preference agreement between the Coalition and the UAP is likely to help Mr Palmer in the Queensland Senate race, where he is competing for a position against One Nation’s former senator, Malcolm Roberts.
The Palmer United Party gained 0.7 of a quota in the Queensland Senate race in 2013 but saw this shrink to 0.2 per cent at the 2016 election after the desertion of former senators such as Glenn Lazarus and Jacqui Lambie.
One Nation gained ground at Mr Palmer’s expense in 2016 by gaining 1.2 quotas, putting Senator Hanson and Mr Roberts in Parliament before he was disqualified for breaching Section 44 of the Constitution.
Candidates require one quota to secure a seat in the upper house, but those who fall short of this may win after gaining second preferences from others.
The Liberal Party ruled out giving preferences to Senator Hanson’s party in the wake of her remarks after the Christchurch terror attacks, making an agreement with Mr Palmer the logical alternative despite reservations about his policies.
Australia Institute director Ben Oquist said the UAP agreement would hurt One Nation but only “at the margins” because preference deals mattered less than in the past because of the Senate voting changes of early 2016.
The changes ended the era of backroom deals between the parties to agree on “group voting tickets” that allocated preferences when voters put a “1” in one box for a single party.
The new system requires voters to number at least six boxes above the line or at least 12 boxes below the line for each party or group.
“It is very likely that if Clive wins it is at the expense of Malcolm Roberts, but it’s not yet clear,” Mr Oquist said.
The Australia Institute findings, based on a national survey of 1426 respondents and another 519 people in South Australia, differ from other polls because voters were asked who they would vote for in the upper house.
The results suggested both major parties have improved their position at the expense of the Greens, One Nation and independent candidates compared to previous similar surveys.
“The recent rise in support for Clive Palmer’s United Australia Party does not put them in position to win a Senate seat at this time,” the report concludes.
“However, if their support continues to rise through to the election, they will be competitive for one or more Senate seats – in particular in Queensland and Victoria.”
The Palmer United Party gained one quarter of a quota in the Victorian Senate race in 2013 but this fell to 0.04 of a quota at the subsequent election.
The Australia Institute concludes Labor will win 28 seats in the upper house while the Greens could win eight or nine, short of the 39 votes needed for a majority in the chamber.
The report, to be issued on Friday, places a range of two to five seats on the One Nation vote and a range of two to three seats on the Centre Alliance vote.
“Unless there is a significant upset with Labor and the Greens winning four seats between them in multiple states, Labor will require the support of one other party: either Centre Alliance or One Nation,” the institute says.
The core projection is that Labor and the Coalition secure two seats each in all states and territories, but that Labor can gain three seats in Victoria.
The projection also allows for the two major parties to pick up some other seats in “competitive” races, depending on the performance of the minor parties.
David Crowe is Chief Political Correspondent of the Sydney Morning Herald and The Age.