Frontrunners, including Liz Truss, the secretary of state; Nadhim Zahawi, the Chancellor; Grant Shapps, the Minister for Transport; and Sajid Javid, the former health minister, all plan to promise to cut taxes as they try to exploit the dividing lines between them and Mr Sunak.
Ms Truss, who is set to launch her campaign on Tuesday, is expected to be on the ticket to reverse Mr Sunak’s controversial social security tax increase, known as the Health and Welfare Contribution.
On Sunday, Penny Mordaunt, the former defense secretary, announced her candidacy after her successor, Ben Wallace, who was the favorite according to some polls, dropped out of the race on Saturday.
Priti Patel, the Home Secretary, is believed to be urged to back Brexiteers but is vying for support with Suella Braverman and Kemi Badenoch, both of whom are becoming increasingly popular on the party’s right.
The Attorney General has already secured the baking of prominent leaver Steve Baker, while Ms Badenoch plans to deliver a campaign speech in the House of Lords on Monday to more than 200 free speech campaigners, including Martina Navratilova and Sharron Davies, both of whom oppose trans women, who compete in women’s sports.
Some believe the number of pro-Brexit candidates who are fiscally conservative could split the vote on the right, giving Mr Sunak momentum.
Richmond’s Lord Hague, Tory leader from 1997 to 2001, was among the senior figures calling for restraint, saying: “The party and the country need calm reflection and a chance for candidates to put forward their positive plans. Conservatives should be careful not to spend their time undermining some of their own leaders.”