Stephen Harper is refusing to say whether he would accept a decision by the Governor General to ask a second-place opposition party to try to form a government in the event another Tory minority fails to gain confidence of the House of Commons.

Harper cited his 52nd birthday Saturday as evidence he has been around politics long enough to know Canadians must choose on Monday between a majority Conservative government or a "risky" NDP-led government propped up by other parties.

AUDIO: The House - The Final Stretch

Former Premier of Ontario David Peterson and former Premier of Saskatchewan Roy Romanow draw on their own experiences to arrive at a few conclusions about this federal election campaign.

During a campaign stop in Richmond Hill, Ont., Harper again appealed to traditional Liberal voters, saying they should be concerned about the stability of Canada's economic recovery and national unity under a Jack Layton-led government.

But when pressed by reporters about what he would do if the next-biggest party was asked to form a government, Harper said he would not speculate about "hypothetical" scenarios following the election.

"We're in this to win, I believe we're going to win; a lot is at stake, every race is close," Harper said.

"What we're doing now is speculating on hypothetical scenarios. We're putting before Canadians the choice that they have, a Conservative government that will keep taxes low and keep the economy moving forward, or an NDP government that will raise taxes, stall our recovery, and set Canadian families back."

The CBC's Terry Milewski faced supporters' boos when he attempted to ask Harper the question again.

In an interview with the CBC's Peter Mansbridge earlier  in the campaign, Harper said said he would not attempt to form a government if another party won the most seats in the election and his party came in second place.

When Mansbridge said the other parties have a right to try to form a government if the Tory government failed to gain the confidence of the House, Harper replied: "That's a question of debate, of constitutional law."

Ontario battleground

Harper's comments came as he and Liberal Leader Michael Ignatieff started the final weekend of the federal election campaign in vote-rich Ontario, while Layton tried to build support in British Columbia.

Harper, who has spent much of the campaign criss-crossing the country urging voters to give him a majority, launched a direct attack on Layton and the NDP, saying the party in power would damage the economy, raise taxes and run higher deficits.

The NDP's platform, he said, "is clearly not the platform of a governing party."

"The risk, and very real risk if we do not win a majority is an NDP-led government like you had in Ontario," said Harper, referring to the highly unpopular provincial New Democratic government of Bob Rae in the early 1990s.

"I feel all people share our view of a strong recovery, low taxes and moving forward and to stay out of some of the other debates the NDP raised," he said. "I encourage all voters who feel that way and who would have traditionally supported the Liberal party to support the consequence for a mainstream party."

Ignatieff, meanwhile, was set to campaign in Guelph, Stoney Creek, Oakville, Mississauga and Brampton on Saturday.

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NDP Leader Jack Layton waves to supporters at a campaign rally in Courtenay, B.C. on Friday. (Andrew Vaughan/Canadian Press)

The Liberals held 37 of Ontario's 106 seats in the last Parliament, and Ignatieff said Friday he's convinced the party's base will turn out to vote on Monday. Ignatieff also said he's aiming to "hoover up" undecided voters in the final days of the campaign.

Layton gains key endorsement

At a campaign event in Kitchener, Ont., on Friday, Ignatieff acknowledged the apparent increase in support for Layton and the NDP.

Ignatieff said Conservatives have focused their attacks on him, targeting everything from his patriotism to his motivation.

"The consequence was, Jack Layton comes up the middle with a big, wide grin."

Ignatieff took repeated aim at the NDP platform Friday, saying a vote for the New Democrats is akin to taking a trip to "fantasy island."

"Choose a platform that actually adds up," he said.

Layton has a single campaign event in Burnaby, B.C. The event comes after the Toronto Star, Canada's largest-circulation daily newspaper, endorsed the New Democrats.

On Friday, Layton blasted a Sun TV News media report citing an unnamed source that he was interviewed by police in a suspected Toronto bawdyhouse in 1996, calling it a "smear campaign."

"It's unfortunate to see the smear campaign starting in these last few days of the campaign," Layton told reporters before a rally in Courtenay, B.C., as recent polls suggest support for his party is surpassing the Liberals.

"Absolutely nothing wrong was done but yet the smears start."

Layton didn’t take reporters’ questions after the remarks, but referred to a statement released earlier by his wife, NDP candidate Olivia Chow, who also denied her husband was involved in any wrongdoing.

Bloc Québécois Leader Gilles Duceppe was to campaign with Parti Québécois leader Pauline Marois on Saturday.

Green Party Leader Elizabeth May, meanwhile, will attend several events in Sidney and Saanich, B.C. May is hoping to defeat Conservative candidate Gary Lunn in Saanich-Gulf Islands.

With files from The Canadian Press