The New Democrats, under leader Rachel Notley, swept all 19 constituencies in Edmonton on Tuesday and made significant inroads in previously barren NDP territory in Calgary, Lethbridge and rural Alberta.
"Friends, I believe that change has finally come to Alberta," Notley, told cheering supporters who chanted "Rachel! Rachel! Rachel!"
"New people, new ideas and a fresh start for our great province."
The NDP, a party that had never won more than 16 seats, captured 53 seats to secure a majority in the 87-seat legislature.
The Wildrose party took second place with 21 seats and will form the official Opposition, while Prentice and his battered PCs were relegated to third with 10 seats.
Liberal Leader David Swann and Alberta Party Leader Greg Clark were also elected. One riding was undecided as PC incumbent Linda Johnson and Anam Kazim of the NDP finished in a tie.
It was a crushing defeat for the Tories, who had steered the ship of state since 1971 — longer than any party anywhere in the country.
Prentice told subdued supporters in Calgary that he was stepping down as leader effective immediately and would also leave the Calgary Foothills seat he just recaptured.
"As leader of the party, I accept responsibility for tonight's outcome. I also accept responsibility for the decisions that led up to this evening," he said.
"Clearly ... my contribution to public life is at an end. It is time for me to dedicate my time to other responsibilities I have as a husband, and as a father and a grandfather."
He took over a party in September that had been stung by scandals under former premier Alison Redford. Legislature members and the premier were using government planes for party business and Redford ordered that a penthouse apartment be built for herself on top of a renovated government building.
The party had also failed to build promised schools and was criticized for lavish salaries and severance payouts to political staff and government executives.
Prentice used his first budget to announce he would not fund growth in classrooms, would cut health spending and would not pay public sector workers a penny more until the books were balanced.
Notley said the election resets the compass.
"Albertans have voted for change and one of the changes that they voted for is a new kind of respect and a new kind of relationship with their government," she said.
"Albertans across the province have told me that they are tired of old, entitled approaches that leave them out of conversations about their livelihoods, about their services and about their families.
"Whether you are a business leader, a union leader, a municipal leader, someone who leads in our civil society or whether you are a plain-old just great wonderful Albertan, let me say this to you: Our legislature belongs to you."
Jean, a former Conservative MP, won his seat in Fort McMurray-Conklin barely a month after he became leader.
The party won 17 seats in the last election, but entered the campaign with just three incumbents after former leader Danielle Smith led a massive floor-crossing to Prentice late last year.
"What a campaign," said Jean to supporters in Fort McMurray.
"It's unbelievable. It was just a few months ago that pundits said the Wildrose Party was dead. We've seen a complete change in Alberta. Wildrose proved them wrong."
He said the key for his party was to focus on its principles and stick to them.
"Albertans ... will not stand for backroom deals, governments that play favourites, or cronyism, or just when it starts to stink a little bit," he said. "When you give away golden handshakes and money that doesn't belong to you, voters won't stand for that."
He said his party is willing to work with Notley "on ideas to reform our government," but will also provide a "fierce opposition," especially when it comes to balancing the budget.
It's the second defeat for Prentice at the hands of the NDP.
He lost to the party in Calgary-Mountain View when he ran for the PCs under premier Don Getty in 1986 before going on to a federal career. He would serve as a cabinet minister in several portfolios under Conservative Prime Minister Stephen Harper.
The Tories were gunning for a 13th consecutive majority when Prentice dropped the writ on April 7.
The election came a year earlier than necessary under Alberta law, but Prentice said it was necessary to gain a mandate to implement his tough budget that proposed sweeping increases in taxes and user fees and cuts in government spending.
He said his goal was to stop Alberta's heavy reliance on fluctuating resource revenue.
While Prentice urged Albertans to be resilient to weather the current storm of low oil prices and job layoffs, Notley was relentlessly upbeat and optimistic during her campaign. She urged people to embrace uncertainty, accept it as a challenge and focus on making life better for families.
It provided a stark choice for voters.
"Albertans needed to make those choices, those decisions, and they have now done so and chosen our collective future," Prentice told his supporters.
"And while I'm personally saddened by the decision, the voters are always right in our democracy."
For Notley, the victory is a vindication of the pioneering efforts of her father, Grant Notley. He helped found Alberta's NDP and kept the movement alive as the sole New Democrat in the legislature in the 1970s and early 80s.
He died in a plane crash in northern Alberta in 1984, two years before his party made its first big breakthrough in 1986 and became official Opposition.
Notley, in her victory speech, talked about her father and her mother, Sandy, whom she credited with instilling in her the importance of public service and speaking out.
"I know that my mother would be completely over the moon about this. I think my Dad would be, too," she said.
"I'm sorry he couldn't see this. This really was his life's work. But ... I know how proud he would be of the province that we all love."
She smiled as her eyes filled with tears as the crowd chanted "Grant! Grant! Grant!"
Prime Minister Stephen Harper has sent his "sincerest congratulations'' to Notley. In a statement issued early Wednesday, Harper said he looks forward to working with "future Premier Notley on issues of importance for Albertans and all Canadians'' such as jobs and economic growth.
He also thanked Prentice for his public service and wished him the "best in his future endeavours.''
B.C. Premier Christy Clark said she's looking forward to working productively with Rachel Notley for a prosperous West. In a statement, Clark congratulated the premier-elect and her team, and also thanked Prentice for his public service.
Clark praised Prentice after he was sworn in as premier last September, promising warm relations after what she called the "frosty" Alison Redford era. She also said at the time that there hasn't been a premier in Alberta's history who understands B.C. as well as Prentice.
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