Boris Johnson and Jeremy Hunt face a gruelling series of 16 hustings across the UK as the final battle for Downing Street gets under way.
The two candidates in the Tory leadership contest have only each other to defeat after Michael Gove and Sajid Javid were eliminated on Thursday.
A series of 16 hustings across the country over the next month will test the candidates before the next Prime Minister is selected. The final leg of the campaign officially kicks off tomorrow in Birmingham.
Admitting he was the underdog to clear favourite Mr Johnson, Mr Hunt nevertheless said: "We are going to give Boris the fight of his life.”
"He needs to be ready for that because we're going to be going out there and making strong arguments that this is the best way to deliver Brexit, with someone who can go and get a better deal from the European Union."
Former foreign secretary Mr Johnson secured support from more than half the Tory party in the Commons with 160 votes.
Mr Hunt received 77 votes and Mr Gove 75.
The result in the fifth and final ballot came after Mr Gove had managed to finish second in the fourth round, sending shockwaves through the contest.
Allies of Mr Hunt urged MPs not to risk the "personal psychodrama" of a run-off involving the Environment Secretary and his rival Mr Johnson.
Mr Gove's decision to stand for the leadership in 2016 scuppered Mr Johnson's campaign and the wounds have not healed.
There was also widespread speculation that supporters of the frontrunner were being encouraged to vote tactically in order to prevent Mr Gove reaching the final ballot.
This was denied by Mr Johnson
Mr Johnson said he was "deeply honoured" by the result and "I look forward to getting out across the UK and to set out my plan to deliver Brexit, unite our country, and create a brighter future for all of us".
Mr Gove said he was "naturally disappointed but so proud of the campaign we ran" and "it's been an honour to be able to set out a vision for the future of our great country".
The final outcome of the leadership contest will not be known until the week beginning July 22, with the two remaining candidates taking part in a series of hustings in front of Tory members around the country before the votes are counted.
Mr Johnson and Mr Hunt will also take part in a head-to-head debate on ITV on July 9.
Labour campaign chief Andrew Gwynne said the country faced a choice between "the man who broke the NHS or the man who wants to sell it to Donald Trump" and called for a general election.
