It is understood that supporters of Treasurer Peter Gutwein are confident they have the eight votes needed to win.

If however, the vote is tied, it's understood a second ballot would be held, and if that were a tie, a break may take place before another ballot.

Some Liberal Party insiders are angry that the leadership is coming down to a vote between Mr Gutwein and Infrastructure Minister Michael Ferguson and would have preferred there to be just one candidate.

Political observers say the fact there is going to be a spill shows how unprepared the Liberal Party was to deal with Premier Will Hodgman's departure.

One observer said they were surprised Mr Hodgman had changed his mind and decided not to vote for his replacement.

"I would have thought he would have wanted the opportunity to have a say in deciding who would continue his legacy and his agenda," he said.

Election analyst Dr Kevin Bonham was unaware of tied ballots for leadership in the past "but that doesn't mean they haven't happened".

"A tied vote is not a good look," Dr Bonham said.

"It will be very close and we're not hearing much noise about how people intend to vote.

"And we know that sometimes people give misleading indications and may change their mind."

Political analyst Professor Richard Herr said in federal ballots with more than one candidate it was a process of elimination.

"With only two candidates in this case essentially there will be 10 votes to decide the leadership.

"If it is tied at seven all you would expect that they would work on the other side's weakest vote."

Professor Herr said if he won by a narrow margin Mr Gutwein might work out a deal similar to the Hawke/Keating agreement that he would hand over to Mr Ferguson.

"But he might have to wait five or six years for that and who knows what will happen in that time," he said.

Party sources say it is a hard decision for the PLP.

"It is like the Howard/Costello vote towards the end - everybody loves both of them and don't want to have to make the choice between them," one Liberal said.

"It may be that they think Peter is 55 (years old) and Michael is 45 and this is the one last shot in the locker for Peter but there is still time for Michael."

Former Liberal MHA Nic Street is likely to replace Mr Hodgman in Franklin.