Jim Wells has endorsed the TUV's South Down candidate Harold McKee against his own party's runner, meaning he could be expelled from the DUP.
Mr Wells has not ruled out joining the TUV, Jim Allister’s party.
Mr Wells told the Belfast Telegraph that he accepted the move could result in him being told to leave the DUP, led by Sir Jeffrey Donaldson.
The former Health Minister said he would have backed Edwin Poots if he had won the nomination for the constituency but he would not support Diane Forsythe.
DUP party officers selected Diane Forsythe as the candidate for South Down in February ahead of Mr Poots, Stormont’s current agriculture minister, who was attempting to switch to the constituency from Lagan Valley.
Mr Poots is now standing in South Belfast.
Mr Wells confirmed to The Irish News that he was now endorsing the TUV's Harold McKee in South Down.
Mr Wells said in a statement: “Harold McKee is the standout candidate and I urge those who supported me in the past to give him their number one preference.”
“As I leave the Assembly it is my earnest desire that South Down should continue to have a unionist MLA whose politics are grounded in conviction and principle.
“Among the candidates, Harold McKee is the standout candidate with these credentials.
“He holds dear many of the core principles that I upheld in Stormont and is widely and properly respected as a politician of conviction rather than expediency.
“Accordingly, I recommend him to those who faithfully supported me at the polls over the years and urge them to vote McKee 1.”
Mr McKee quit the Ulster Unionist Party last year, claiming Doug Beattie's leadership was at odds with his religious beliefs.
Newry, Mourne and Down District councillor Harold McKee, who in 2016 briefly served as the UUP's South Down MLA, criticised Mr Beattie for advising members to "leave their Christianity at the door".
He attacked his former party leader over his stance on abortion, same-sex marriage and a recent vote at Stormont on gay conversion therapy.
His resignation statement said Mr Beattie's leadership was "a far cry from the UUP roots, which the leader described as being ‘the party of Carson and Craig'".
