CALGARY -- Stephen Harper's tenure as Canada's sixth-longest serving prime minister came to an abrupt end Monday night as his party was reduced to opposition status and he prepared to step down as its chief.

Harper is staying on as an MP for his own riding of Calgary Heritage, but will now look to his party to reach out to his shrunken parliamentary caucus to request they choose an interim replacement.

"The prime minister indicated that he will continue to sit as a member of Parliament and asks that a process to both select an interim leader and initiate the leadership selection process in our party begin immediately," Conservative president John Walsh said in a statement.

He went on to say the party's national council would set out new rules and logistics for a leadership race, and that a "transparent process" would be established to review the 2015 campaign.

A policy convention had been scheduled for this May in Vancouver, and that will need to be postponed.

Oddly, Harper left it up to Walsh to deliver the news he would be stepping down as leader. His concession speech made no mention of it, short of acknowledging responsibility for the night's resounding defeat.

"While tonight's results is certainly not the one we had hoped for, the people are never wrong," an animated, upbeat-looking Harper told supporters in his concession speech.

"The disappointment you also feel is my responsibility and mine alone. But know this for certain: when the next time comes, this party will offer Canadians a strong and clear alternative based on our conservative values."

Harper's departure will signal the beginning of a tumultuous time in the party -- he has been the only leader of the organization formed in 2003 between the Progressive Conservative and Canadian Alliance parties.

Monday night's results were being described as a bloodbath by party loyalists who watched in disbelief as cabinet ministers were getting wiped off the electoral map by a surge of Liberal support that also saw the party steal long-held Conservative ridings across Atlantic Canada, Quebec and Ontario.

Rare bright spots emerged in Alberta, where Defence Minister Jason Kenney and Health Minister Rona Ambrose held on to their ridings -- two names considered possible contenders to lead a party that will be doing a lot of soul-searching come Tuesday morning.

Kenney deflected questions about his future but acknowledged the party is entering a dark time.

"It's a bad night for the Conservative party but we'll come back," he said. "I think on substantive points, we've been a very good government; where we went wrong was on tone."

The Conservatives knew they were facing a tough election when Harper chose to start the clock in August, nearly a month earlier than anticipated. But what the party wasn't prepared for was a collapse of NDP support that would see the Liberal tide rise and drown Conservative hopes across the country.

And the grousing about what happened and who should shoulder the blame has already begun.

"On every issue, polling shows Canadians are with the government. Two things happened: a bad campaign and Harper fatigue," said one Conservative source, speaking on the condition of anonymity because they weren't authorized by the party to comment publicly on the results.

Complaints ranged from local campaigns not getting the preparation and support they've received in past campaigns to a failure by the Conservatives to campaign more effectively on their record -- as opposed to just attacking the Liberals.

Others said the change narrative being presented by the other parties was just too strong for Harper to beat back.

"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."

At the Calgary Convention Centre, where Harper was expected to address supporters, about 400 chairs were filled with supporters, family and friends; dozens more stood around to watch the results.

"This doesn't make me happy at all. I think there's been a lot of smearing of Stephen Harper," said Susan Garvey, who drove down from Red Deer, Alta.

"I am very upset. I think there's been a lot of lies told about Stephen Harper and I don't think Trudeau is anywhere near ready to run this country. I think Stephen Harper has done such an excellent job and I can't fathom why anyone would not vote for him."

Many headed directly to the bar to drown their sorrows.

"Got any Kleenex?" asked Byron Schwandt, who was wearing an "I'm a Harperman" T-shirt.

Eighteen-year-old Tyler Van Vliet, a University of Calgary student who was carrying a 'Harper for Canada' sign, said he wants Harper to stay on the job.

The Conservative leader did a lot of good things for Canada over the past decade, said Van Vliet.

"Unfortunately people forgot that going into this election. There's still those of us who appreciate what he's done."

In the final days of the campaign, Harper had refused to discuss his own political future after election night, saying only it's been an honour to serve as prime minister for nearly 10 years.

- With files from Jennifer Ditchburn in Toronto and Bill Graveland in Calgary.