Edwin Poots is to challenge a DUP decision not to select him as the party's election candidate for South Down, close ally Jim Wells has said.
And Mr Wells said he would consider running against the DUP as an independent if the move to choose Diane Forsythe is not overturned.
Party officers on Friday night selected Ms Forsythe instead of former DUP leader Mr Poots, who was attempting to switch to the constituency from Lagan Valley.
Mr Wells expressed confidence that the wider party executive will block the decision and install Mr Poots as the candidate when it meets next week.
Mr Poots has told colleagues he has no plans to revert back to contesting his seat in Lagan Valley, where DUP leader Sir Jeffrey Donaldson and First Minister Paul Givan are set to run for the Assembly.
The Agriculture Minister was "extremely disappointed" with the outcome of Friday's selection meeting, sources close to Mr Poots told the BBC.
They claimed there were prior discussions with Sir Jeffrey and that Mr Poots was of the understanding he would receive the nomination for South Down.
But other party sources rejected this, saying there was no prior agreement.
South Down MLA Mr Wells, who was deselected as the DUP's candidate for the constituency, said it was "not game over yet" for Mr Poots.
"He's very disappointed, but determined to go on," Mr Wells told the BBC's Nolan Show.
"He just said he's terribly disappointed. He also said, 'I'm going on, I'm fighting this. I'm going to gain support from the central executive committee, and I believe I can overturn this decision', and I believe he can.
"And certainly the associations that I have spoken to are solidly behind him. So it's looking encouraging."
The DUP has been facing an electoral headache in Lagan Valley with three of the party's biggest names potentially running in the same constituency where it currently holds two seats.
Mr Poots and Mr Givan currently represent Lagan Valley in the Assembly, while MP Sir Jeffrey is also seeking a return to Stormont in the constituency.
Mr Wells said that after being deselected he approached Mr Poots about switching to South Down.
"I am absolutely mystified as to why he (Mr Poots) wasn't selected," he told PA.
"I thought it was important that we had an experienced candidate and they don't come much more experienced than Edwin Poots.
"I just assumed that he would be selected. Four times a minister, former party leader, former party vice chairman, so therefore I was absolutely gobsmacked on Friday night when he wasn't."
The DUP executive, which is made up of more than 120 people including including MPs, MLAs and delegates from each constituency association, will meet next week to ratify election candidates.
Mr Wells said: "I am determined to get Edwin Poots selected at the central executive committee, and then I'll be campaigning for him."
Asked what he would do if Ms Forsythe is ratified as the DUP candidate for South Down, he said: "The phrase I have is: no plans to run as an independent, but I will keep options open."
Pressed on whether he was ruling out running as an independent, he said: "I would consider it, but I have no plans at the minute to run as an independent."
Speaking of Ms Forsythe, he said: "She doesn't have the same view of the way forward as I have, it is as simple as that.
"Edwin would be more traditional and would be old-fashioned DUP, which I am."
Mr Wells found out earlier this year that he had not been selected as the party's candidate for the South Down, which he has represented since 1998.
He said: "I am deeply hurt that it has ended this way. Deeply hurt. But naive in thinking that it would be any different."
