On his final campaign flight from Abbotsford, B.C. to Calgary, Stephen Harper sat with his closest friends and began putting together the plan for his exit from the Conservative Party leadership.

That plan will unfold this week, as Conservative politicians and the party's rank-and-file look to a future leadership race — only the merged party's second — putting the pieces in place to move forward and rebuild from a devastating election loss.

Public Works Minister Diane Finley speaks during question period in the House of Commons on Parliament Hill in Ottawa. Sources say Finley could be tapped to be the interim leader of the Conservatives. (Adrian Wyld/Canadian Press)

Harper was calm about the defeat that lay before him, according to sources who spoke to The Canadian Press over the past 24 hours. He sat alternately with longtime aide Ray Novak, and party president John Walsh on the plane.

There are two main things that will happen right away — Harper will resign as leader, but stay on as an MP. The party's much smaller caucus will vote for an interim leader. Former cabinet minister Diane Finley's name is an early name being floated.

Then, the party's national council will appoint a "leadership election organizing committee," which will set the ground rules for the impending contest.

'Harper's party' facing upheaval

All these things will send the party into a period of upheaval — this was the party Harper built, filling positions with loyalists over the years to such an extent that there was barely a murmur of discontent in 12 years.

At the same time as the leadership race is set in motion, the activists are in the process of sorting through the embers of the campaign, analysing what went wrong and who is to blame.

The party's executive director, Dustin van Vugt, is in charge of a process to review the campaign.

A senior party source said the party will be in debt after this election is through, something the members aren't used to.

As far back as Thursday, campaign manager Jenni Byrne was packing up her office in the Ottawa party war room. In a sign of how tense things have become inside Harper's circle, Byrne was not in Calgary on election night, and is out of a job as of Monday morning.

During the campaign, sources say longstanding friction between Byrne and campaign director Guy Giorno just became worse, and the two strong personalities clashed on elements of the campaign. One insider said Byrne refused to hand over a list of candidate contact details to Giorno in the final days.

Bad blood among top aides

Eventually, their hostility spilled over into bad blood between Byrne and Novak, who is the person Harper trusts the most.

Party sources say Jenni Byrne doesn't deserve all the blame for the Conservative Party's failed campaign, because she managed the victory in 2011. (Sean Kilpatrick/Canadian Press)

"There's a tremendous amount of antipathy towards her on the part of the leader," said one source.

"You don't run a campaign by surrounding yourself by sycophants, interns and family members," grumbled another.

But there are different ideas of why the campaign did not succeed. Some point to failings in the nuts and bolts organization of the campaign, while others believe the problems centred around the leader himself and his choice of message — factors no local candidate could control.

A source close to the war room said the party's focus groups and voter research had told them that the die was cast before the campaign began. Conservative voters "were sick of the PM and had a hard time voting for him."

"The feeling from Jenni as the campaign manager is that this was lost from the get go," said the source, who asked to remain anonymous.

"They underestimated people's feelings about the PM, that there was a stronger desire for change than they realized."

Dan Miles, a senior aide to outgoing finance minister Joe Oliver, said it was clear in the riding that voters were looking for change. Oliver lost his Eglinton-Lawrence riding in a near Liberal sweep of the Greater Toronto Area.

"The only negative I really ever heard was that they liked Joe, but they had a problem with the leader," said Miles.

"That was the only consistent thing I ever heard."

Meanwhile, the leader's message on the economy wasn't resonating as well as they suspected. The Liberals ate into some of that territory with voters who liked the promise of infrastructure spending. Liberal Leader Justin Trudeau performed better than expected during the debates.

The niqab issue raised by Harper dealt a blow to NDP Leader Tom Mulcair in Quebec, but it also seemed to wound the New Democrats elsewhere.

"That policy and so many others resonated positively with some voters, and negatively with others," Oliver said in a scrum.

"I think that, and maybe some other policies, were responsible for the collapse of the NDP, which had a very significant impact on the national results."

Jason Kenney: We needed 'sunnier' conservatism

Calgary Conservative MP Jason Kenney, widely believed to be a serious leadership contender, alluded to problems with the party message. Trudeau had focused on optimism, while Harper issued dire warnings of bleak economic times and terrorist threats.

Conservative MP Jason Kenney holds a news conference to discuss the NDP's spending plans, in Ottawa. Kenney says the campaign needed to promote a 'sunnier' brand of conservatism. (Fred Chartrand/Canadian Press)

"We need a conservatism that is sunnier and more optimistic than what we have sometimes conveyed," Kenney said.

"We have to take collective responsibility for that."

On the other side, there are those who believe the party's losses can be attributed to poor preparation.

That would include the training of local volunteers, the recruitment of candidates, convincing incumbents to run again, and vetting candidates. The conclusion is that the party didn't take enough advantage of natural advantages of being in power, of having a huge war chest and its wealth of experience from previous campaigns.

"In this case I fear that, like all parties in power, we got fat and happy," said Chad Rogers, a party loyalist who volunteered during the 2006 campaign, then run by the late Doug Finley.

"This campaign was not as lean, as focused or as aggressive as the ones that preceded it. A lot of candidate and campaign managers that I've been talking to informally were very surprised that things we were good at, just weren't done this time."

Rogers said there would be questions asked about how money was spent, especially the abandoning of a new, multi-million voter identification system two years ago.

Other Conservatives said the party hasn't kept up with the times on the latest research methods and technology.

The source close to the war room said that it will be unfair to lay the blame all on Byrne, who also led the successful 2011 campaign.

"She's a lightning rod, partly because of her personality, but also because she's a woman," said the source. "She's going to bear the brunt of a lot of knifing because she's a woman at the top of the food chain."