Britain's new prime minister: Who will it be and when does the term begin?

The United Kingdom will find out Monday whether Rishi Sunak or Liz Truss will take over as party leader and prime minister. Truss is expected to win. 

Boris Johnson’s brief but tumultuous tenure as prime minister ended after he voluntarily stepped down following one crisis too many even for a man once touted as "Teflon-coated." In the weeks that followed, various members of his party and cabinet tossed their hats in the ring or discounted themselves from the running. 

The months-long race to take top seat in the party — and one of the most powerful positions on the planet — finally ended with a party-wide vote. Any paid-up member of the party, including those who live overseas, had to submit a ballot Sept. 2 to have a say on which of the two remaining candidates will succeed Johnson. 

The chairman of the 1922 committee, composed of Conservative Party backbenchers, will announce the result of the vote Monday. 

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THE LEADERSHIP RACE

Alan Mendoza, executive director of the Henry Jackson Society, told Fox News Digital there was "no doubt" Truss would win, and that a Sunak win would be "nothing short of a miracle." 

"I think when it came to the party, it was obvious very early on that [Sunak] wasn't the favorite, simply because the language Liz Truss has spoken is speaking more to where the Conservative Party wants to be," Mendoza explained. "I think there's been a reaction against, say, the big spending and, you know, high taxation of the Boris Johnson government." 

From the most diverse group of candidates for a party leadership vote in British history emerged Sunak, the 42-year-old former chief secretary of the Treasury and chancellor of the Exchequer, and Truss, the 47-year-old secretary of state for foreign, commonwealth and developmental affairs. 

Sunak had led the charge on ousting Johnson when he and Sajid Javid, former secretary of state for health and social care, resigned almost simultaneously. The did so in response to Johnson defending his decision to appoint Conservative MP Chris Pincher as deputy chief whip despite Johnson later admitting he knew about complaints of sexual misconduct against the minister. 

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Truss stood in stark contrast to Sunak and continued to support Johnson until the moment he announced he would step down as prime minister. 

TRUSS V. SUNAK

Each minister took a different tack to try and convince the party they had the vision for the future of the country. Sunak focused on the soaring inflation in the U.K., while Truss promised to cut taxes as soon as she took office. 

Sunak also focused on restoring "trust" to the leadership following Johnson’s many scandals. 

But Truss’ loyalty to Johnson, as well as her tax-based approach to dealing with growing financial hardships, appears to have paid dividends. Sunak’s early and commanding lead faded, leaving Truss the clear front-runner, according to most analysts.

"What Liz Truss is saying is that even though she was a foreign faction, she is saying, look, give me the opportunity and I will cut taxes and give more liberty to you, and I think that's a message that's been very popular with the grassroots of the party," Mendoza argued.

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PARTY VOTE

Nile Gardiner, director of the Margaret Thatcher Center for Freedom, noted that Sunak’s lead in the first round of voting came from members of parliament while the last round includes the wider roughly 200,000-person party membership, which would skew more toward Truss’s more hard-line approach. 

"I think you can see that the party membership, the grassroots of the Conservative Party, is largely to the right of the parliamentary party as a whole, and Liz Truss has run as the Thatcherite candidate," Gardiner told Fox News Digital. "The vast majority of Conservative Party members are of the right, and they have overwhelmingly backed Liz Truss, according to the polling.

"Rishi Sunak is definitely on the center of the Conservative Party, is not a Thatcherite politician." 

Members had the option of voting by mail or, for the first time, casting an online ballot. The National Cyber Security Center (NCSC) branch of British intelligence delayed an earlier vote planned for the start of August due to hacking concerns in the voting system – a concern that many cybersecurity experts continued to raise until the deadline, according to The Guardian newspaper. 

"We do not have the technology to conduct voting securely online, and so it should not be deployed for high-stakes elections," Peter Ryan, a professor of applied security at the University of Luxembourg,  told The Wall Street Journal. "And I count this as rather high stakes … For the moment, short of a major conceptual breakthrough, I don’t see how it can be done." 

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TAKING POWER

Once the party announces the winner, the changeover should happen swiftly. Johnson will officially resign on Tuesday morning, and the new party leader will take office – with a small twist. 

"For the first time in her reign, Her Majesty won't be in London or Windsor to invest the new prime minister but in Scotland," Mendoza noted, highlighting concerns over mobility issues as the 96-year-old monarch vacations in Balmoral. "Then, the winner has to go to Scotland as well to be sworn in. And then immediately they've got to get to work, obviously, with choosing a cabinet and then lower ministerial ranks." 

Turnover in the cabinet remains a mystery, though some select ministers, including Defense Secretary Ben Wallace, should remain in their posts to provide some sense of continuity. Gardiner suggested that as many as 80% of the cabinet positions might see have members. 

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But analysts expect the new government to commence Wednesday with all posts filled. 

"What we understand is there will be a cabinet meeting on Wednesday morning and a big speech," Mendoza said.