North Belfast MP Nigel Dodds has ruled himself out of the contest to succeed Peter Robinson as leader of the DUP.
The 57-year-old deputy leader of the party said he had given "prayerful thought" to his position.
Mr Dodds backed Arlene Foster "to take the party and Northern Ireland forward".
Mr Dodds said he believed he was not best placed to lead the party, as he is not currently a member of the Stormont Assembly.
The long-serving MP, whose wife Diane is a European MP, said he felt "humbled" by those who had supported the idea of him taking over.
However, he said he felt it would be wrong to put his own personal standing ahead of what he thought was best for the DUP.
The party's MLAs, MPs and MEP are due to meet to select the new leader in an east Belfast hotel next week.
Mr Robinson, 66, announced his intention to resign last month, days after signing a political deal with Sinn Fein and the British and Irish governments to stabilise the rocking powersharing administration in Belfast.
Mrs Foster is a current MLA so if she was elected leader there would be a degree of expectation that she would become First Minister as well.
Last week Sammy Wilson also ruled himself out of running and backed Dodds to take the helm.
Mr Dodds said: "Following Peter’s announcement that he was stepping down as leader and First Minister I have been giving much prayerful thought to my own position and what is in the best interests of the party.
"For a long time I have been consistent in my belief that, with devolution now firmly established in Northern Ireland, I would only put my name forward for leader if I was a member of the Stormont Assembly.
"I am previously on record as stating clearly my view about the disadvantage of attempting to lead a modern Northern Ireland party from Westminster when we now have devolved government. Indeed I have previously made my view known in discussions with senior colleagues.
"I have been humbled by the expressions of support from many quarters in recent days and therefore have taken time to reflect further.
"I remain of the view that being at Westminster means I would not be able to devote the necessary day to day focus and time to the role of leader and, at the same time, properly and fully carry out my duties and responsibilities in the House of Commons.
"The work and the opportunities for Northern Ireland at Westminster have already grown significantly and especially recently as a result of the DUP’s position in a House of Commons where the Government has such a small majority. That work and those opportunities are only set to increase over the course of the five years of this Parliamentary term.
"I am conscious too that my wife Diane is also fully committed in her work as an MEP.
"Whilst in other circumstances it would be natural and a great honour to lead the party, it would be wrong in my current circumstances to put my own personal standing above what I believe to be the long term best interests of the party and the people we serve.
"I believe that in the Assembly Arlene Foster is the leader that can take our party and Northern Ireland forward to an even better future.
"I will continue to fulfill my duties to the party as Deputy Leader and working together as part of a strong team of DUP representatives at every level we will continue to offer the best opportunity to advance the cause of unionism at Stormont and Westminster."