Prime Minister Stephen Harper could call an election as early as this weekend, sources tell CTV News, which would trigger one of the longest federal campaigns in Canadian history.

Voters head to the polls on Oct. 19, but the official campaign won’t start until Harper visits Governor General David Johnston and asks him to dissolve Parliament.

So far, Harper remains tight-lipped on when that might happen.

“I don't speculate and I particularly don’t speculate on my own actions,” he said Wednesday in an interview with Bloomberg.

The Elections Act requires a campaign to be a minimum of 36 days, but there’s no set maximum. The last federal election had a 39-day campaign.

If the writ is dropped this weekend, it would mean 11 weeks of campaigning. The record for the longest campaign in modern Canadian history is the 1926 election, which lasted for 10-and-a-half weeks.

And the longer the campaign, the more costly for taxpayers. An extended campaign would cost millions of dollars more.

Conservative MPs were already fanning out across the country this week to making funding announcements, as the party gears up for the official campaign start.

Employment and Social Development Minister Pierre Poilievre visited Kitchener, Ont., to publicize the government’s Universal Child Care Benefit -- even directing his message to children at summer camp.

“Now that we’ve balanced our budget, we can help your mom and dad balance their budget,” he said.

Minister of State John Duncan made a dozen announcements on Wednesday alone.

“You can’t be making announcements during an election period, so this is the window that’s open,” he told CTV News during a stop in Lake Cowichan, B.C.

Meanwhile, NDP Leader Tom Mulcair has already been campaigning steadily in vote-rich Ontario.

CTV News pollster Nik Nanos said Mulcair’s strategy appears to be paying off.

“What has effectively happened is Stephen Harper and Justin Trudeau have ceded the platform to Tom Mulcair and he’s taking advantage of it,” Nanos said. “It’s kind of like starting a marathon an hour ahead of your competitors.”

Liberal Leader Justin Trudeau is expected to start campaigning next week.

With a report from CTV’s Deputy Ottawa Bureau Chief Laurie Graham