Now, with the government in tatters, bookmakers and much of Britain are speculating about his likely successor. Any candidates who run for the leadership will go through rounds of voting by Conservative lawmakers until only two remain — at which point Conservative Party members nationwide will vote. The winner will be the new party leader — and prime minister.
Here’s a look at the potential contenders.
The former chancellor was Johnson’s presumed successor for several months after he won praise for overseeing Britain’s initial financial response to the Covid-19 pandemic.
But he has suffered several of his own scandals while in government.
His financial and legal affairs came under scrutiny this spring following reports his wife had non-domicile status in the UK — meaning she was not liable to pay tax on overseas income — and that he held a US green card while serving as minister.
“This week again, we have reason to question the truth and integrity of what we’ve all been told. At some point, we have to conclude that enough is enough,” the former health secretary told the House of Commons on Wednesday, referring to the appointment of and allegations linked to Pincher.
Something is “fundamentally wrong” with government, he added, and “the problem starts at the top.”
But those who support Javid’s candidacy hope that he will be credited for triggering Johnson’s ultimate ouster, having been the first cabinet minister to resign — though Sunak followed him minutes later.
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.
She has a formidable and dedicated team around her — some of whom previously worked in Number 10 — which has been producing slick videos and photos of her looking thoroughly statesmanlike. She has apparently attempted to channel former Prime Minister Margaret Thatcher, wearing a headscarf while driving a tank, and her role in fronting the response to Russia’s invasion of Ukraine has also heightened her public profile.
Truss is popular among Conservative members, who would pick the eventual winner of a contest. But Johnson’s downfall could simultaneously tarnish anyone in his cabinet, meaning Conservative voters could turn to a backbencher to take the mantle.
Last month, a source working in the Foreign Office told CNN that Truss had been in “endless meetings with MPs,” and that “it’s been insinuated that she’s seeing what her support base is, should the time come.” Truss’s office denied that any covert leadership bid was coming.
Mordaunt first entered parliament in 2010 and later joined the cabinet under Theresa May, serving as international development and defense secretary.
He outlined his vision for tackling the cost of living crisis, reducing taxes and investing in neglected regions of the UK.
Despite not having any cabinet or shadow cabinet experience, Tugendhat has impressed colleagues with his oratory skills and seriousness, most notably when he spoke about the fall of Afghanistan. He entered parliament in 2015 after serving in the Iraq and Afghanistan wars.
Some key centrist Conservatives have already been throwing their support behind the relative wildcard, but some worry that his experience is too focused on foreign affairs.
Until his promotion, Zahawi, who joined the cabinet less than a year ago, was considered an unlikely choice as the next prime minister. But his rise under Johnson has been rapid, making his mark with early success as vaccines minister amid the coronavirus pandemic and then as education secretary.
Despite voting to leave the European Union in 2016, Zahawi is widely admired among the moderates in the party. Crucially, as one Conservative source put it, “he’s not been in government long enough to have any obvious defects and, despite supporting Boris even after the confidence vote, is not too tainted by association.”
Zahawi was born in Iraq to Kurdish parents and came to the UK at 9 years old, when his family fled Saddam Hussein’s regime. He is believed to be one of the richest politicians in the House of Commons, and helped found the polling company YouGov.
In a statement on Twitter ahead of the confidence vote in June, Hunt said: “Anyone who believes our country is stronger, fairer & 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.”
Tellingly, Hunt’s statement focused mainly on the Conservatives’ chances of electoral success under Johnson, rather than his policies or the partygate scandal — a decision that could be read as a pitch to the Tory MPs and members who would decide a leadership election. However, he comes with baggage, and sources from the opposition Labour Party have told CNN they are already writing attack lines.
“It can’t be Jeremy. Labour can say he was running healthcare for six years and failed to prepare for a pandemic. They can say when he was culture secretary he chummed up to the Murdochs during the phone hacking scandal. He will get crushed,” a senior Conservative source told CNN.
Other possible contenders
CNN’s Jorge Engels in London contributed to this report.