Tory contender: Stephen Crabb
Date of Birth: 20 January 1973
Job: Work and pensions secretary
Education: Tasker Milward comprehensive school in Haverfordwest, Pembrokeshire; Bristol University
Family: Married with a son and a daughter
On his party's future: Pitching himself as a unity candidate, who can heal divisions caused by the referendum campaign.
"I love my country, I love my party, and I genuinely believe that what I stand for, the values that I represent, the strengths that I bring are exactly those that are required to get us through the challenges ahead." Running on a joint ticket with Business Secretary Sajid Javid, who would become chancellor if Mr Crabb wins the contest. The pair have promised to scrap the Tory government's tight borrowing rules to set up a £100bn fund for new infrastructure, to be paid for by a bond issue.
Where he stands on Brexit: He campaigned to remain in the EU but now says: "We had a clear result from the referendum. And the result was for the UK to leave the European Union. There can be no stepping back from that." Has ruled out a second referendum.
Mr Crabb has set out three aims for the EU negotiations: Controlling immigration, "as close an economic relation with the EU as we have now" and "end of the supremacy of EU law".
When he would trigger Article 50: Has cautioned against rushing into it, saying he would take a "few months" to allow the "dust to settle".
Free movement policy: Has promised no more "open borders" but wants continued access to the EU single market, a goal he admits will be "very challenging" to achieve. Has said he would not use EU citizens living in the UK as "negotiating chips" when forging a new post-Brexit deal with the EU, assuring them that they would be allowed to remain - even if other EU countries threatened to remove UK citizens.
What the press says: "Blue collars are all the rage in the Tory party these days, which makes Stephen Crabb a very fashionable cabinet minister. It's no surprise that he has just been named the successor to Iain Duncan Smith: his back story is perfect, and is driven by the same social justice agenda. He was brought up in a Welsh council house by his mother, a single parent. His political views were shaped by seeing the way in which Thatcher's reforms transformed his neighbourhood. He still believes Conservative values give the best hope for working-class and Welsh voters. As the Tories led an ever-deeper raid on Labour territory, it was inevitable that we would see and hear a lot more from people like Stephen Crabb," says Isabel Hardman in the Spectator
A former marketing consultant, Mr Crabb's background - he grew up on a council estate in Haverfordwest, raised by a single mother - contrasts with the more privileged upbringings of others on the Conservative front bench.
Backers include Scottish Tory leader Ruth Davidson, who told a newspaper earlier this year she would "find it very hard to vote for anyone else".
Mr Crabb says his first political memory is the 1979 general election that brought Margaret Thatcher to power, and that witnessing her flagship right-to-buy policy on his street had a "huge impact" on him growing up.
After attending Tasker Milward school in Haverfordwest, he studied at Bristol University, gaining a first-class degree in politics and joining the Conservative Party after graduating.
He won his seat at the second attempt in 2005, and worked as a whip before becoming a minister in the Wales Office, where he was appointed secretary of state in July 2014.
In 2013, he voted against same-sex marriage legislation for England and Wales.
Asked about it as he launched his campaign, he said it was "not an issue", having now been decided, adding: "I'm absolutely committed to doing my bit to create a tolerant, decent society for everybody regardless of their background, regardless of their sexuality."
Following the resignation from the cabinet of Iain Duncan Smith over disability benefit cuts, Mr Crabb, the first Conservative cabinet minister for a century to have a beard, was promoted to work and pensions secretary.
At the time of the appointment, many saw his personal story as well suited to the role.
In a previous interview with BBC Wales Westminster correspondent David Cornock, the MP for Preseli Pembrokeshire described how the welfare system provided a "genuine safety net at a time of crisis" for his family.
"I had a mother who, as we got older, moved progressively from a position of complete welfare dependency to being fully economically independent, working full-time," he said.
"And that has to be the model of the way the welfare system should work."
Married to French wife Beatrice, with two children, Mr Crabb lives near Haverfordwest.
A keen rugby player, he still turns out for the Commons and Lords RFC.