A University of Otago professor has suggested that Boris Johnson's reign as Britain's Prime Minister could be a "colourful and brief" affair - if he beats Jeremy Hunt.
Voting closed at 5am NZT in the two-man contest to become the next Prime Minister, as critics of likely winner Mr Johnson condemned his vow to take the UK out of the European Union with or without a divorce deal.
The winner is expected to be announced at 10pm this evening and take over from departing incumbent Theresa May tomorrow.
Mr Johnson, a populist former mayor of London, is the strong favourite.
Several members of Ms May's government have said they will resign before they can be fired by Mr Johnson over their opposition to his threat to go through with a no-deal Brexit if he can't secure a renegotiated settlement with the EU.
Speaking this morning to TVNZ1's Breakfast programme, University of Otago historian and professor Robert Patman said that Mr Johnson, if he wins, will be in for a tumultuous time.
"I think it could be colourful and brief," Mr Patman said.
"Mr Johnson is facing some really difficult problems and what he's promised, while it appeals to 0.3 per cent of the population - that's the 160,000 largely white males that are electing him as leader of the country - what they want and what the rest of the country wants is quite different.
"What Mr Johnson is going to find out is that the two key promises he's made - that he's going to re-negotiate the deal or he's going to take Britain out of the EU without a deal - he can't deliver on.
"So he's going to have to improvise and probably come up with some new initiatives rather quickly."
Mr Patman described Mr Johnson as a "political maverick" whose real motivation is "power".
"When he ran for London mayor, he was cosmopolitan, outgoing and pro-immigration," Mr Patman said.
"When he decided to bid for leadership of the Tory Party, he embraced Brexit - he saw that as a vehicle to becoming leader - so he's quite unpredictable in that sense."
Mr Patman said his prediction is that Brexit will not happen at all, despite Mr Johnson having "another stab at it".
"Amongst the Brexiteers, the problem was that Ms May was not a true believer," Mr Patman said.
"Mr Johnson says he is a true believer - we're going to find out.
"It takes more than acts of faith and belief in the inherent superiority of Britain to achieve the sort of deal he wants with 27 other liberal democracies that make up the EU.
"He could face parliamentary stalemate quite quickly.
"He has hinted that he will suspend parliament in order to force through a no-deal solution, but parliament will not allow that, so it seems to me that he's going to face deadlock quite quickly.
"He faces really tough problems, and I don't see that he's indicated anything so far on how to solve them credibly."