The Tory leadership contest will enter the next stage later when a second round of voting is held in Parliament.
Conservative MPs will vote by secret ballot in the Commons, with a result expected some time after 18:00 BST.
Any of the six remaining candidates will be eliminated from the contest if they come last or fail to secure at least 33 votes.
Those remaining in the race will take part in a live BBC debate in central London on Tuesday evening.
Remaining candidates will face further ballots later this week, where the bottom-ranked MP will be knocked out until only two candidates are left.
The final two names will then be put to a postal vote of the 160,000 Tory party members, beginning on 22 June, with the winner expected to be announced about four weeks later.
Former Foreign Secretary Boris Johnson remains the clear frontrunner in the race after topping the first ballot earlier this month with 114 votes.
Former cabinet minister Andrea Leadsom – who was knocked out of the race at the first ballot – has given Mr Johnson her support.
Speaking on LBC, she said Mr Johnson was “an election winner” who was “best placed” to take the UK out of the EU by 31 October.
Current Foreign Secretary Jeremy Hunt, who came second with 43 votes, and Environment Secretary Michael Gove, who was third with 37, should make it through to the next ballot on Wednesday if their support holds firm.
Former Brexit Secretary Dominic Raab, who received 27 votes, and Home Secretary Sajid Javid, who received 23, told reporters on Monday they were confident of making it through to the next round.
International Development Secretary Rory Stewart, who received 19 votes in the first ballot, said he had the necessary 33 backers to stay in the race “if they do what they say”.
