A Conservative victory is, however, not certain, as one-third of Canadians still say they are unclear of how they will vote.
Longest minority rule
Harper was elected with a minority for the first time in January 2006 and managed, by some calculations, to have the longest minority government in Canadian history.
He called the election on September 7 to seek a renewal of his mandate to govern.
Speaking in the town of Cornwall, Prince Edward Island on Monday, Harper said: "The number one job of the next prime minister of Canada is to protect this country's economy, our earnings, savings and jobs at a time of global economic uncertainty."
"If you give me the honour of re-electing me as your prime minister, I can assure you that I will make it my top priority to protect Canada's economy and Canadians' stake in it," he said.
Meanwhile, Dion called on voters to "stop Stephen Harper," saying the prime minister "has no plan" to safeguard Canada's economy from the worldwide problems provoked by a collapse in the US subprime mortgage market.
"We have a plan to create jobs, to ensure that we are doing all we can in these tough economic times to protect our pensions, our savings, our mortgages, and our jobs," he said.
Polls at the start of the campaign had Harper winning a majority government, but he then hurt himself politically when he said during a debate that Canadians were not concerned about their jobs or mortgages.
Days later, he said stocks were cheap. Canada's main stock exchange then had its worst week in almost 70 years.
Harper has since tried to undue the damage by saying that he knows Canadians are worried.
"The number one job of the next prime minister of Canada is to protect this country's economy"
Stephen Harper, Canada's Prime Minister
He contrasted Canada's economic and fiscal performance to the more dire situation in the US
"Americans are running deficits. We're running surpluses. Americans are incurring debt. We're paying down debt," Harper said.
"We have the lowest unemployment rate in 30 years ... We have a better economic situation than the United States because, for two and a half years, we have made better choices."
Harper has maintained that Canada will avoid the mortgage meltdown and banking crisis that are hitting the US and Europe.
Harper's government announced last week that it will buy up to US$21 bn in mortgages from the country's banks in an effort to maintain the availability of credit.
Canada's economy has fared better than that of many of the other Group of Seven (G7) industrialised nations.
Unlike the US and the UK, banks in Canada are not in danger of collapse.
However, around 75 per cent of Canadian exports go south to the US and in the past - such as in 1975, 1982 and 1991 - when the United States' economy shrank, so did Canada's.