Liz Truss or Rishi Sunak will be named as the next leader of the Conservative Party and succeed Boris Johnson as the Britain's next prime minister on Monday.
The two have been campaigning for six weeks after Johnson announced his resignation following a slew of scandals and resignations from his government.
Truss, the current Foreign Secretary, is widely considered the frontrunner, with opinion polls putting her well ahead of former Finance Minister, Sunak.
What will the prime minister need to address first?
Whoever emerges as the winner faces "the worst in-tray for a new prime minister since Thatcher," The Sunday Times wrote, referencing former Prime Minister Margaret Thatcher.
Top of the list will be tackling the United Kingdom's cost-of-living crisis.
Thanks to global gas price volatility triggered by the war in Ukraine, the average UK household energy bill is jumping to more than 3,500 pounds ($4,000; €4,041) a year. The UK faces decades-high inflation and is tipped to enter recession later this year.
Truss on Sunday promised to take "decisive action to ensure families and businesses can get through this winter and the next."
"If elected, I plan within the first week of my new administration to set out our immediate action on energy bills and energy supply," she wrote in the Sunday Times.
She has signaled during her leadership campaign that she would challenge convention by scrapping tax increases and cutting other levies.
Sunak, who sought to paint himself as a more realistic economist, said he would temporarily cut the value-added tax on energy bills. He emphasized, however, that he wouldn't "max out the country's credit card,'' and said significant tax cuts should wait until inflation is under control.
What foreign policy issues face the UKs new leader?
The new prime minister will also have to steer the UK on the international stage with Russia's war in Ukraine, an increasingly assertive China, and ongoing tensions with the European Union over the aftermath of Brexit toping that agenda.
Truss, said she would tear up parts of the Northern Ireland Protocol, a step that could lead to a trade war with the EU.
A bill to unilaterally scrap some customs checks to ease the movement of goods is working its way through the British parliament, and Truss said last month that if picked as prime minister she would seek to deliver that legislation in full.
Sunak, has said he would "push on" with the legislation while still trying to negotiate with the EU.
How will the prime minister will be announced?
The Conservative Party will announce which candidate won the most votes from party members after two months of campaigning. The announcement on Monday sets in motion a chain of events.
On Tuesday, Johnson will deliver a farewell speech at Downing Street. Johnson and his successor will travel to Scotland to meet with Queen Elizabeth II.
He will formally tender his resignation, and the Queen will appoint his successor in a so-called kissing of hands ceremony.
The new leader will fly back to London to deliver a speech outside Downing Street and appoint a cabinet.
On Wednesday, the prime minister will face their first head-to-head Prime Minister's Question Time with the leader of the opposition Labour Party, Keir Starmer in Parliament.