Hemel MP Mike Penning will be part of the inside team when Home Secretary Theresa May announces her bid to become the leader of the Conservative Party today.
Mr Penning, who has represented the town since 2005, has worked closely with Mrs May since he became minister of state for policing and criminal justice after last year’s general election.
But he said that his motivation for joining the team was simple: He thinks that she is the best candidate for the job.
Mr Penning said: “I think that Theresa May is more than willing and able to bring the party together and the country together.
“She has huge experience of negotiating with the EU, and she’s one of if not the most successful Home Secretaries of all time.
“I’ve campaigned against our membership of the EU for my whole political career and perhaps that meant people assumed I’d go for Boris Johnson.
“But frankly I think that the country needs someone like Theresa with her experience and stature.”
The leadership election has been sparked by David Cameron’s resignation Prime Minister following the EU referendum.
Mr Cameron had campaigned for the UK to stay in Europe, and stepped down after his defeat.
Although Mrs May also sided with the Remain camp, her support was widely rumoured to be lukewarm.
Mr Penning has worked closely with Mrs May in recent years in his role as a junior Home Office minister.
He added: “Theresa is straight-talking, well-respected and knows what she wants.
“She doesn’t like ‘yes men’, she wants to be challenged - she’s what we need in a Prime Minister.”