Maverick Tory candidate Rory Stewart has been knocked out of the contest to choose the next Conservative leader.
It means the four remaining candidates are former Foreign Secretary Boris Johnson; Environment Secretary Michael Gove; Home Secretary Sajid Javid, and Foreign Secretary Jeremy Hunt.
Conservative MPs held the latest in a series of votes, and Mr Stewart came last - which means he has been eliminated from the contest.
He began the election as an outsider, despite holding a Cabinet post as International Development Secretary, but won support thanks partly to his innovative use of social media.
Mr Stewart filmed himself out and about at locations across the country and invited people to “meet, talk and challenge” him, using the hashtag #rorywalks.
His perceived weaknesses included his plan, if he became Prime Minister, to convince MPs to back the same Brexit withdrawal deal negotiated by Theresa May that they have already comprehensively rejected.
He also attended the same school as Boris Johnson, Eton. It means that if he and Mr Johnson both made it through to the final stage of the contest, it would have been a battle between two old Etonians who also both attended Oxford University.
MPs will continue voting in the leadership contest on Thursday June 20, until there are only two candidates left.
The final two will then take part in the second stage of the election, a vote of Conservative Party members.
A series of hustings events will take place across the country, with the first in Birmingham on Saturday June 22.
And the winner will be announced on Monday July 22. They will automatically become Prime Minister.
In theory, the contest could end sooner if a candidate withdraws voluntarily.
The results of the latest round of voting by MPs were:
Michael Gove - 51
Jeremy Hunt - 54
Sajid Javid - 38
Boris Johnson - 143
Rory Stewart - 27
In a televised debate on Tuesday evening, Mr Johnson said the October 31 deadline for Brexit was "eminently feasible".
But Mr Hunt accused the former foreign secretary of lacking clarity on whether he guaranteed getting the UK out of the EU by the end of October.
He told BBC Radio 4's Today programme: "Well, I am not entirely sure what he believes on this, having listened to him last night.
"You have to think these things through because prime ministers have to make these judgments."
