Days after a jubilant Greg Clark revealed a former NDP MLA was joining his caucus, the Alberta Party leader was summoned to a special conference call with the party's executive and board.

Clark had a hint that something was about to change, though he never expected to tender his resignation that afternoon, thus triggering a leadership race, sources have told CBC News.

In fact, at the time Clark, had his eye on other prospects he hoped would make his two-MLA party grow further in the legislature.

For weeks, he had been in discussions with newly independent MLAs Rick Fraser and Richard Starke, two progressive former PC MLAs who sat behind him in the legislature.

Both Fraser and Starke had refused to join the new United Conservative Party caucus after Jason Kenney became leader in early November, heading up the new conservative entity that folded former PC and Wildrose members into one party.

Clark reminded reporters as he strode into question period on Nov. 6 that he was hoping to increase the size of his caucus by at least convincing Fraser to join the Alberta Party.

Just two days later, the Alberta Party executive and board asked to talk to Clark.

Sources told CBC News that by then the fix had been in about Clark's leadership for weeks, perhaps months.

Calls not returned

The centrist Alberta Party had experienced a surge in memberships, including former PC members unhappy with the direction the UCP was taking under Kenney.

In the weeks leading up to the conference call, key people in the Alberta Party had stopped returning Clark's phone calls, sources said, and even those behind the newly formed centrist political action committee, Alberta Together, had gone dark.

That gave Clark a hint something was up.

After the conference call, friends urged Clark to consider his options for continuing in the leadership, and not to rush or be pushed into making a hasty decision.

They reminded him about the soaring memberships, and the fact he had built the party profile from near obscurity. There was also a sold-out annual general meeting coming up in Red Deer.

Though he didn't have constituency associations set up in each Alberta riding, Clark had attracted a new MLA, former Calgary-Mackay-Nose Hill NDP member Karen McPherson.

'It's a train wreck'

"He was backed into a corner" on being squeezed out of the leadership, a source close to Clark told CBC. "He's taking the hit and saying it's his idea, because he doesn't want to destroy the Alberta Party. But it's a train wreck."

Clark put on a brave face and soldiered on.

That evening, he reluctantly agreed to an already scheduled interview with a media outlet tipped to his story.

Political strategist Stephen Carter says he presented a plan to the Alberta Party board and leader Greg Clark that resulted in a leadership race. (CBC)

Political strategist and operative Stephen Carter, who works as a volunteer with the Alberta Party, said he had no direct role in shaping Clark's decision.

However, Carter, who has a lengthy political resume, including both campaign failures and successes, said he did put forward "an argument" to Clark and the board during the conference call.

Carter said he told them there were only two opportunities for a party to grow significantly; first, during a leadership race; and second, during competitive candidate nominations.

"I said I didn't think they would get to the second if they didn't do the first, so they wound up doing the first," Carter said.

Despite that, Carter insisted the decision to resign was Clark's alone.

"I made the argument to Greg, I made the argument to the board," Carter said. "Greg decided that was the right argument."

Clark said he resigned for the benefit of the party, though he thinks he could have taken the party to the next level.

"We need to take a risk, to take a step up in what the Alberta Party is," Clark told reporters. "This was my choice."

Clark acknowledged the idea of him leaving the leader's job had been talked about for "months and months as an option."

But he refused to say whose idea it was for him to resign following the board meeting on Nov. 8.

Former Alberta Party leader Glenn Taylor, who has remained active in the party since he resigned in May 2013, said Clark's departure was baffling.

'I was disappointed'

"I was disappointed," Taylor said in an interview from his home in Hinton.

Taylor said he watched with amazement as Clark suddenly announced publicly he was stepping down, leaving those who first formed the party wondering what happened.

"I think he did a heck of a job for us," said Taylor, noting that when Clark was the only party MLA he produced a shadow budget and attracted a new MLA.

"Although I understand why he did it (stepped down)," Taylor said, "I'm disappointed he went that route."

Taylor said he hopes Clark seeks the leadership again, and will support him if he does.

Going forward, Taylor said he's encouraged by the growing interest in the party, and rejected the notion expressed by some that is a hostile takeover by former PCs.

"We've always believed the progressive side of the PC party really belongs with the Alberta Party," said Taylor.

'He was pushed out'

Carter worked on Clark's unsuccessful Calgary-Elbow provincial byelection campaign in 2014.

He said he supports Clark's decision to step down, and hopes he runs for the leadership again.

The Alberta Party has set Feb. 7 as the date when the new leader will be announced. But there are no details yet about how voting will take place, how much it will cost to enter the race, nor are there any declared candidates.

Clark said he hasn't decided if he'll enter the contest. But he's adamant he'll be an Alberta Party candidate in the next provincial election, currently expected in 2019.

Government house leader and Transportation Minister Brian Mason has seen plenty of political manoeuvres play out over the years. To him, it's clear what happened with Clark.

"I've been around politics for a long time, and it looks like he was pushed out by a bunch of PCs that were basically taking over his party," said Mason.

The late PC premier Ralph Klein often said "politics is a blood sport."

"I've called it that, too," said Mason.