A split has already emerged in the cabinet of outgoing Prime Minister Liz Truss about who its members want to lead the Conservatives.
Some of the key cabinet names publicly backing frontrunner Rishi Sunak are:
Home Secretary Grant Shapps
International Trade Secretary Kemi Badenoch
Work and Pensions Secretary Chloe Smith
Others who have declared their support for Boris Johnson are:
Levelling Up Secretary Simon Clarke
Northern Ireland Secretary Chris Heaton-Harris
Alok Sharma, COP26 President
Chancellor of the Duchy of Lancaster Nadhim Zahawi
Transport Secretary Anne-Marie Trevelyan
Source: BBC