Either foreign secretary Liz Truss or former chancellor Rishi Sunak must grapple with the cost-of-living crisis, the war in Ukraine, strained public finances and a series of other issues that will make any sort of political honeymoon almost impossible.
After a race that has lasted the summer, the successor to Boris Johnson will have no time to get comfortable.
Ms Truss, who is almost certain to win, is believed to have planned a series of big event within the first 30 days.
This is understood to include two major fiscal events, several policy speeches, meetings with world leaders and, of course, putting together a new Cabinet.
Here are the immediate challenges facing the new leader in their first month in charge.
The most pressing concern is the economic crisis, which is considered the worst since the 2007/08 global financial crash.
Energy bills are soaring, inflation is in double digits, and some experts are predicting a ten-year recession.
Having already gone from £1,971 to £3,549, average energy prices could then reach more than £6,000 by the spring.
While the Government has offered a £400 payment to every household and tax cuts have been promised, charities warn this will not be enough.
They say failing to announce a more substantial package could push millions into destitution, and people will die.
Personal finance expert Martin Lewis has called the crisis a “portentous national cataclysm”.
The new prime minister will need a new plan by October, or face telling a public who cannot afford to cook food or heat their homes they should wait it out.
Ms Truss this week ruled out energy rationing in the winter, despite it being openly discussed both by the Department for Business, Energy and Industrial Strategy and the National Grid.
An emergency budget has already been promised, with a second fiscal event also now under discussion in the form of a spending review later in the year.
The first 30 days will see the new prime minister make their debut foreign visit at the annual UN General Assembly in New York, opening for world leaders on September 19.
This will be an opportunity to rally support in the international community, not least from US president Joe Biden.
The Ukraine crisis is not going anywhere anytime soon, and working with the international community to maintain support for the Western response will be crucial.
This will mean holding talks with the EU over a unified approach.
Ms Truss is not popular in Russian from her role as foreign secretary, with Russian foreign minister Sergey Lavrov previously saying meetings were “like talking to a deaf person”.
She has also promised a review of defence priorities following Russia’s invasion of Ukraine.
Meeting with Mr Biden will also be important for Brexit, with both Mr Sunak and Ms Truss committed to pushing forward with legislation to rewrite the Northern Ireland protocol.
This risks a trade war with Brussels, and Washington fears it would be damaging to the Good Friday Agreement.
Then there is the UK’s position on continued membership of the European Court of Human Rights, which is essential for the Northern Ireland protocol and security elements of the UK-EU Trade and Co-operation Agreement.
Both candidates have refused to rule out quitting the body, which the EU say would be a deal breaker for the trade arrangement.
Whoever becomes prime minister will need to decide on their relationship with the EU quickly.
After a bruising leadership contest, Ms Truss will hope to bring the party back together and rebuild their fortunes in the polls.
The new prime minister will make ministerial appointments tomorrow and Tuesday after being appointed, with a host of allies set for promotions.
Ms Truss’s old friend Kwasi Kwarteng is set for chancellor, while close allies Thérèse Coffey and Simon Clarke are also expected to get big jobs.
Mr Sunak may be offered health secretary, as is tradition, but has already suggested he would turn it down amid criticism of his rival’s financial plans.
Ms Truss has already committed to including Kemi Badenoch in her top team.
Her Cabinet would need to be in place in time for the first Prime Minister’s Questions on Wednesday.
Senior officials will also be appointed on Tuesday, including chief of staff, director of communications and head of the No. 10 policy unit.
Recently-appointed No. 10 deputy chief of staff David Canzini is expected to be among those who will stay, with staff told there will be a degree of continuity in the new regime.
The UK Government’s approach to Scotland is less of an immediate problem and more an ongoing one.
Ms Truss has vowed to maintain the role of minister for the Union that Mr Johnson created, and will hope to do more with it.
She will hope to meet with First Minister Nicola Sturgeon sooner rather than later and, before resigning, Mr Johnson had agreed to a cost-of-living conference with the leaders of the devolved administrations.
Then there is the small matter of the Supreme Court battle over independence, with Lord Advocate Dorothy Bain QC referring a prospective referendum Bill to the Supreme Court in July to ascertain if it was within the powers of the Scottish Parliament.
With the court case taking place next month, Ms Truss will have plenty of time to prepare for the question that will not go away.