"We're going to need a slightly bigger phone booth!" beamed leader Brian Mason as he spoke to enthusiastic supporters, who chanted his name and cheered as the results came in.
The four seats — all in Edmonton — are twice what the NDP had going into the campaign — enough for official party status and the extra resources that come with it.
"It doubles our voices," Mason said.
"That gives us the opportunity to be that voice that stands up in the legislature for public health care. We forced (Progressive Conservative Leader) Alison Redford during the campaign to say she would not privatize health care and we are going to hold her to that."
Mason, the oldest of the four major party leaders at 58, began the campaign on an elder statesman note.
Five days into the race, he chided his rivals for what he called a "negative tone" in exchanges between Progressive Conservative Leader Alison Redford, Wildrose Leader Danielle Smith and top Liberal Raj Sherman. He made the point in letters written to each of them.
On Monday night, he suggested that the Conservatives benefited from voter concerns about comments from some Wildrose candidates that were widely seen as anti-gay and racist.
"What disturbed me is not that they had some people among their candidates that had those views, but that Danielle Smith would not distance herself from them," said Mason. "That bothered me and it probably bothered a lot of other voters as well."
Mason conceded that the NDP might have wielded more clout if the vote had left them with the balance of power. But he promised to work with the government that Albertans elected — and warned the Tories and Wildrose that he expects the same from them.
"There's certainly been a lot of animosity between the PCs and the Wildrose, and that was evident in the legislature. I think it's up to both of those parties to approach the public's business in a mature and responsible way."
Mason's campaign occasionally jumped outside the box of New Democrat orthodoxy. He offered the campaign's only tax cut, a proposal to drop the rate on small businesses to two per cent from three.
Other proposals sounded more familiar from a left-of-centre party.
Taxes on large corporations and wealthy individuals would go up. Electricity rates would be re-regulated. The tax system would be rejigged to encourage energy companies to upgrade oilsands bitumen in Alberta instead of being shipped south of the border.
Mason promised Alberta seniors a break on prescription drugs that would cap out-of-pocket expenses at $25 a month. He also repeated a long-standing New Democrat commitment to increase the number of long-term care beds and pledged public funding for dental care for children under 18.
He scoffed, with characteristic bluntness, at Smith's assertion that the science behind climate change remains unsettled: "It's only disputed by phoney scientists funded by the oil industry," he said during the last leaders debate.
Mason's party has had an up-and-down relationship with Alberta voters.
In the late 1980s, the party had 16 seats and enjoyed the support of nearly one in three voters. A few years later, in the 1993 election, the New Democrats were wiped out and garnered only 11 per cent of the popular vote.
Mason, now in his third campaign, tied his best showing from 2004, when his party also won four seats.
The result means Albertans are likely to hear more from the man who's been in public life since 1989, when he quit his job as an Edmonton bus driver to run for city council.
"We're going to have a renewed NDP opposition in the legislature," he told supporters.
"We have put the party back in NDP and that's what we're going to do now."
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