"I was confident we were going to win," Stelmach said Wednesday when asked about the election by reporters following a legislature social function.
"(But) as with any election you wait for the other team to do something that I'm quite sure today they're questioning, (which were) some of the comments about climate change."
"When you're going to put somebody on an international stage to sell this province, you better listen to your customers around the world before you draw a line in the sand."
Stelmach, premier from 2006 until he retired and was replaced late last year by Alison Redford, didn't run in the past election but helped out candidates by knocking on doors.
He said what he was hearing from voters on the doorsteps was drastically different from the provincewide polls that suggested Smith's party was set to end the Tories' 41-year hold on government.
Smith's team started strong in the month-long campaign but faltered near the end when Smith reiterated the party policy that stated while the Wildrose would still work to reduce the carbon footprint, the science of global warming was not settled.
Stelmach said the voters agreed Alberta would have a big problem selling oil and promoting environmental stewardship on the world stage with a premier who didn't believe in climate change.
"We definitely heard it at the doors," he said.
"These are serious matters.
"You're going to go to Europe today and tell them you don't believe in climate change and you're going to sell them oil?"
"You don't have to believe it or disbelieve (climate change). That's not the issue. Your customer is demanding it. So if you're selling black suits and your customer wants white, what are you going to do? Convince them black is white? Doesn't happen."
The Wildrose also had to deal with controversial comments made by two candidates during the campaign: one criticized public schools for preaching tolerance of homosexuals while another said that as a white man he would be listened and respected by people of all races.
Smith distanced herself from the comments but refused to toss the candidates out of the race. She said she believed in free speech, but stressed those views would never become Wildrose policy.
Stelmach said regardless of public concern over the comments, it was still the greenhouse gas issue that delivered the mortal self-inflicted wound.
Redford's Tories won 61 of 87 seats to secure a 12th consecutive majority government.
The Wildrose won 17 seats, over half of them in the rural southern ridings, to become the official Opposition. Smith won her seat in Highwood, south of Calgary.
The Liberals took five seats and the NDP four.
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