Upper: from left, Former finance minister Rishi Sunak, Former defence secretary Penny Mordaunt and Foreign Secretary Liz Truss. Middle: from left, Opposition party s leader, Keir Starmer, Chancellor of the Exchequer,Nadhim Zahawi, and Ex-health secretary Jeremy Hunt. Lower: from left, Attorney General Suella Braverman, Tom Tugendhat, Army reservist officer, and Junior foreign office minister Rehman Chishti
Here is a selection of the candidates' declarations so far, heading into a meeting later Monday of a committee of Tory MPs to set the contest's ground rules:
"I want you to know how sad I am to be giving up the best job in the world, but them's the breaks," Boris Johnson fires the starting gun on the race in his resignation speech Thursday.
I'm Not Boris
"Let's restore trust, rebuild the economy and reunite the country," former finance minister Rishi Sunak, who helped push Johnson out, launching his campaign in a big-budget video on social media.
The hugely wealthy Sunak, a devoted family man and observant Hindu, also warns his rivals against offering "comforting fairy tales" instead of hard truths.
"Our leadership has to change. It needs to become a little less about the leader and a lot more about the ship," Royal Navy reservist and former defence secretary Penny Mordaunt, in an equally slick video.
Problem is, the video has unauthorised footage of individuals including a clip of a race featuring South African Paralympian Oscar Pistorius, who was jailed for murdering his girlfriend.
The New Thatcher?
For months before Johnson's announcement, Foreign Secretary Liz Truss has been on leadership manoeuvres, channelling some of Tory icon Margaret Thatcher's signature photo-ops from the 1980s.
Her Thatcherite pitch is to "bring down the size of the state and the tax burden", vowing to cut taxes "from day one" so as to tackle Britain's cost-of-living crisis.
Truss is not alone. Tax cuts are an article of faith for most of the leadership contenders, leading to more than £200 billion ($240 billion) of unfunded commitments promised thus far, according to the Labour party.
The opposition party's leader Keir Starmer is set in a speech later Monday to attack the "arms race of fantasy economics" developing in the ruling party.
Sunak's successor Nadhim Zahawi is an eager combatant in the arms race, insisting the current tax burden is "too high", even as he takes stock of his vast new portfolio as chancellor of the exchequer.
But Zahawi has his own tax issues: reportedly, the multimillionaire is under investigation by officials in his own Treasury department over his past business affairs. He says he is being "smeared".
The Sunday Times reports at least two of the campaign teams have passed "dirty dossiers" onto Labour, compromising allegations against rivals ranging from personal finances to drug-taking and use of prostitutes.
"I am the only major candidate who has not served in Boris Johnson's government," ex-health secretary Jeremy Hunt, who has allied himself with a populist MP from northwest England to try to expand his appeal.
"I called out what was going wrong long before any of the other major contenders and I have not been defending the indefensible."
From the "anti-woke" right of the party, Attorney General Suella Braverman says that owing to the energy crisis amid the war in Ukraine, "we must suspend the all-consuming desire to achieve net zero by 2050".
She vows to deliver on "all of the great opportunities" of Brexit, as well as taking a "firm line" on migration.
Another leadership contender trawling the same waters, Kemi Badenoch, hits out at "identity politics" and says Johnson was "a symptom of the problems we face, not the cause of them".
Famously, when asked in 2017 what was the naughtiest thing she'd ever done, the straight-laced then prime minister Theresa May answered "running through fields of wheat" as a child.
Tom Tugendhat, an Army reservist officer who served in Iraq and Afghanistan, was asked the same question as he presented his own leadership pitch. He replied: "I invaded a country once."
Rehman Chishti, newly installed as a junior foreign office minister in Johnson's lame-duck cabinet, is barely a household name in his own household, according to wags.
But he tells Tory members in a Facebook video that he has "a proven track record" of ideas. The video was shot on a smartphone, features loud wind noise, and ends abruptly with Chishti in mid-sentence.