Also in the running are MLAs Paul Frew of North Antrim and Paula Bradley of North Belfast.
Nominations for both the leader and deputy leader of the party closed at 5 pm today, Thursday, May 6.
There are two candidates for the DUP’s top job – Agriculture Minister Edwin Poots and Sir Jeffrey Donaldson MP.
The deputy leader post became vacant after Lord Dodds announced on Tuesday that he would not bid to remain in the post.
Party officials have said candidates should not give interviews about their candidacy in the first-ever DUP leadership contest.
Mr Campbell is the most senior and well-known of the three candidates.
He joined the DUP shortly after it was founded in the 1970s.
He has been a councillor and an MLA but he is currently MP for East Derry, having first won the seat 22 years ago.
He has faced criticism in the past for making remarks about the Irish language that were described as “ignorant” by Sinn Fein.
Mr Campbell is also a supporter of a number of evangelical groups.
Earlier this year, he was accused of “race-baiting” after describing the number of black people on an edition of Songs of Praise as “the BBC at its BLM (Black Lives Matter) worst”.
He refused to apologise but said he was opposed to racism “in all its forms”.
Mr Frew has been the MLA for North Antrim since 2010, while Ms Bradley has been the MLA for Belfast North since 2011.
A majority of the 28 DUP MLAs and eight MPs have not made any public declarations of support concerning the leadership race.
Agriculture Minister Edwin Poots is said to be the favourite to become DUP leader.Tags: