OTTAWA  Prime Minister Stephen Harper, putting aside the date he had set by law, formally propelled Canada into a federal election campaign on Sunday.

The vote on Oct. 14 will come about a year earlier than the date Mr. Harper had specified in legislation after his Conservative Party assumed power in January 2006. It will be the third national election for Canada in just over four years.

Mr. Harper asserted that opposition parties had forced his hand by rendering Parliament “dysfunctional.” But his opponents retorted that the early vote was exactly the sort of political manipulation the prime minister had promised to eliminate.

“We have come to the moment that requires the people of Canada to choose the way forward,” Mr. Harper said outside Rideau Hall, the residence of Governor General Michaëlle Jean, who as official head of state formally dissolved Parliament and set the election in motion. “They will choose between direction or uncertainty, between common sense or risky experiments, between steadiness or recklessness.”