Where to begin with the man who seemingly called his "Leave" companion Boris Johnson's bluff to throw his hat into the ring?
Gove was a strident and divisive Education Secretary from 2010 to 2014, overseeing a radical expansion of the academies programme to give schools freedom from local authority control, while nevertheless insisting they focus on core academic subjects.
Gove was adopted at the age of four months. As Education Secretary, he introduced reforms to speed up the adoption process and was criticised for prioritising adoption above alternative placement options for children removed from their birth families.
He had started to apply his reformist zeal to the post of Justice Secretary, which he has held since the 2015 general election. After reversing a ban on prisoners receiving books, in September he ordered a review of the youth justice system to assess whether existing arrangements are fit for purpose.
In the wake of allegations of mistreatment of children at Medway Secure Training Centre he also vowed to transform the culture of STCs and to give them the same amount of support as "ordinary schools".
Voting records in the House of Commons show Gove consistently voted for ending financial support for 16- to 19-year-olds in training and further education. He also generally voted for equal gay rights and almost always voted for allowing marriage between two people of the same sex.
Education Secretary Nicky Morgan is one of the MPs to have pledged her support to Gove's leadership campaign.
Home Secretary since 2010, May is the current favourite. One of her earliest acts at the Home Office were to oversee the closure of the previous government's ContactPoint database of children and young people and the abolition of antisocial behaviour disorders.
May and her department clashed with Gove and the Department for Education in June 2014 over concerns about the DfE's handling of allegations of extremism in Birmingham schools and where responsibility for the problems resided.
She introduced gang injunctions as part of a series of measures to deal with the fallout of the 2011 riots, sought to address the rise of radicalisation and extremism and introduced government support in tackling violence against women and girls.
She combined the role of women and equalities minister between 2010 and 2012 alongside being Home Secretary. In opposition, she was shadow family secretary between 2004 and 2005 and shadow education secretary between 1999 and 2001.
Voting records show that May generally voted against university tuition fees, while most Conservative MPs generally voted for. She voted a mixture of for and against equal gay rights and consistently voted for allowing marriage between two people of the same sex.
Childcare and education minister Sam Gyimah is among those MPs backing May for the leadership.
Crabb was appointed Work and Pensions Secretary in March after Iain Duncan Smith resigned apparently in protest against cuts to disability benefits.
Raised by a single mother on a Welsh council estate, Crabb has in fact worked in the youth sector. He became parliamentary affairs officer at the National Council for Voluntary Youth Services in 1996, where he is said to have established weekly policy bulletins and campaigned for volunteers to be exempt from paying for CRB checks. Between 1995 and 1997 he was also a volunteer youth worker at a community project in Bermondsey, South East London.
In 2009, he spoke in parliament about "the importance of youth activity" and "youth leaders" in tackling gangs and serious youth violence.
Voting records show Crabb voted consistently for university tuition fees and almost always voted for academy schools. He also generally voted against equal gay rights and voted against allowing marriage between two people of the same sex.
Indeed, he has been criticised for his links with Christian Action Research and Education a group that has reportedly advocated "conversion" or "reparative" therapies for young homosexuals.
Leadsom is the "dark horse" of this leadership contest. Relatively unknown in the country until she campaigned for "Brexit" during the referendum campaign, she has now emerged as second favourite behind Theresa May.
She has been energy minister since the 2015 general election and for a year prior to that was economic secretary to the Treasury.
Leadsom is a strong advocate of boosting the life chances of young children She has chaired the all-party parliamentary group on Sure Start. During the general election last year she locked horns with representatives from Labour, the Liberal Democrats, the Green Party and Ukip during a 4Children debate about boosting support for children in their early years.
In 2013 she was quoted saying that children's centres should be a "core part of the public sector infrastructure" in local communities, and given statutory status like schools.
She also has an interest in the links between maternal mental health and children's outcomes, having founded the charity Northampton Parent Infant Partnership in 2011 and being chair of the Oxford Parent Infant Project for nine years.
Voting records show she consistently voted for university tuition fees and almost always voted for academy schools.
Former children's minister Tim Loughton is one of the more notable backers of Leadsom's campaign.
A former Army medic, Fox has held a number of posts in his parliamentary career from Defence Secretary in 2010/11 to shadow health secretary in 1999 to 2003.
He is founder of charity Give Us Time, which takes holidays donated by holiday groups, hotels and time shares, and matches them with military families in need of rest, respite and reconnection.
Fox has been critical of abortion and has called for "huge restriction, if not abolition on the UK's pro-abortion laws".
Voting records show Fox generally voted against equal gay rights and against allowing marriage between two people of the same sex. He also generally voted for academy schools.
He stood unsuccessfully for Conservative leadership in 2005.