Rivals of Britain's beleaguered prime minister have been working behind the scenes to succeed him as crises after crises have overwhelmed him in recent months.
Following the "partygate" scandal, which involved unauthorized gatherings at Downing Street that were held in defiance of coronavirus lockdowns, a number of senior members of Johnson's cabinet started covertly preparing for a potential leadership race. They courted powerful lawmakers and enjoyed meals with potential campaign donors.
On June 6, Johnson survived a vote of confidence, but more than 40% of Conservative legislators said they no longer believed he could rule. Those who wanted to see his downfall the most have been vying for his job over the past month.
On Tuesday, Health Secretary Sajid Javid and Chancellor of the Exchequer Rishi Sunak quit over the careless handling of the resignation of Johnson's former deputy chief whip in a sexual misconduct scandal. Both prominent parliamentarians had been expected to enter the race.
Here are the potential candidates:
Rishi Sunak
In a polished campaign film, the former chancellor on Friday officially declared his candidacy to succeed Johnson. The movie opened with the tale of his Indian parents, who both immigrated to the UK from East Africa. He claimed that "Britain, our nation, gave them and millions of others the prospect of a better future." "I want to guide this nation in the correct path."
For some months after receiving accolades for leading Britain's early financial reaction to the Covid-19 outbreak, Sunak was widely seen as Johnson's replacement. But while in office, he experienced a number of his own scandals.
His stock took a hit earlier this year after it came to light that he violated Covid rules by going to the prime minister's birthday party on June 19, 2020. He later issued a "unreserved" apology.
Following revelations that his wife had non-domicile status in the UK, which exempted her from paying tax on foreign income, and that he possessed a US green card while serving as a minister, his financial and legal issues came under investigation this spring.
He is still one of the heavy favorites to replace Johnson, though, according to the bookmakers.
Sajid Javid
Sajid Javid's resignation address, which outlined how to reform the party for future generations, had a strong ring to it of a bid for prime minister. Only a few days later, he began his campaign to succeed Johnson.
In a statement published on Twitter on Sunday, Javid stated that he was running for the position of Conservative Party leader because the next prime minister "requires integrity, expertise, and a tax-cutting plan for economic growth."
Javid was the first cabinet minister to resign, though Sunak soon joined him minutes later. Those who support Javid's candidacy expect that because he was the first, Johnson's eventual removal will be attributed to him.
The MP has twice run for party leadership in the past -- in 2016, after the Brexit referendum, and in 2019, when Johnson was ultimately elected.
Liz Truss
The foreign secretary, who has made her aspirations for the presidency public recently, might now be in the lead. Although Liz Truss supported Brexit in 2016, she has subsequently emerged as one of the government's most vocal opponents, which many attribute to her ambition to become prime minister.
She is surrounded by a strong and committed crew, some of whom have worked in Number 10, who have been creating slick videos and pictures of her looking absolutely statesmanlike.
Wearing a headscarf and operating a tank in an apparent attempt to emulate British Prime Minister Margaret Thatcher, she has also raised her notoriety by leading the international reaction to Russia's invasion of Ukraine.
Truss is well-liked by Conservative members, who would choose the final contest winner. However, Johnson's fallout may also bring discredit to anyone in his cabinet, which would lead Conservative voters to look to a backbencher to assume the role.
Penny Mordaunt
The trade minister, who is one of the betting favorites to succeed Johnson, declared her candidacy for the presidency on Sunday. She came in second in a party member survey conducted by the website Conservative Home on July 4, behind current defense secretary Ben Wallace.
In 2010, Penny Mordaunt became a member of parliament for the first time. She later joined Theresa May's cabinet and was appointed defense and international development secretary.
Mordaunt refused to say if she supported Johnson after the confidence vote last month, and when she said: "I didn't choose this prime minister," onlookers in Westminster raised an eyebrow.
She stated that the party's leadership "has to become a little less about the leader and a lot more about the ship" when declaring her interest in the top position.
Tom Tugendhat
Tom Tugendhat, a former British military officer who currently serves as the chair of the Foreign Affairs Committee, has been one of Johnson's most vociferous detractors and has urged the Conservative Party to stop focusing on "divisive politics."
Tugendhat declared in The Telegraph on Thursday that he was running for prime minister: "I have served before — in the military, and now in Parliament. Now I aim to answer the call once more as prime minister. It's time for a clean start. It's time for rebirth."
He described his plan for addressing the housing issue, cutting taxes, and putting money into underserved areas of the UK.
Nadhim Zahawi
Johnson was publicly called to quit less than two days after Nadhim Zahawi was named chancellor to succeed Sunak. He accompanied a letter to the prime minister with a remark on Twitter that read, "Do the right thing and leave now."
Zahawi, who entered the government less than a year ago, was regarded as an improbable candidate for the position of next prime minister prior to his promotion. However, under Johnson, he rose quickly, first earning a name for himself as the minister in charge of vaccines during the coronavirus outbreak and later as the secretary of education.
Jeremy Hunt
Jeremy Hunt, a former health and foreign secretary, was defeated by Johnson in the 2019 leadership election. He has now positioned himself as Johnson's opposite and is without a doubt the most well-known candidate on the moderate, pro-Remain side of the party.
"Anyone who believes our country is stronger, fairer, and more prosperous when led by Conservatives should reflect that the consequence of not changing will be to hand the country to others who do not share those values. Today's decision is change or lose. I will be voting for change," Hunt wrote on Twitter ahead of the June confidence vote.