Ottawa Centre has been called one of the safest NDP ridings in the country after Paul Dewar won with more than 50 per cent of the vote in 2011, but Liberal candidate Catherine McKenna has called for strategic voting in the hope it will swing her way.

McKenna has argued that the best way to ensure the Conservatives do not get re-elected is to make sure the Liberals gain enough seats — including NDP seats like Ottawa Centre.

It does seem the New Democrats are concerned over the question of strategic voting in that riding. - CBC Poll Analyst Eric Grenier

"We need to beat the Conservatives in the seat count if we're going to get them out. If Stephen Harper wins by just one seat, we could be back to the same old politics," McKenna says in a new social media video.

Just two months ago, critics scratched their heads, wondering why the Liberals were running a high-profile candidate against Dewar — but now the mood has shifted.

CBC poll analyst Eric Grenier's vote projection threehundredeight.com put Dewar eight points ahead on Friday, but his share of the predicted vote has dropped from more than 50 per cent to 40 per cent since the campaign began.

"Ottawa Centre is a riding the New Democrats would have considered one of their safest in the country at the beginning of the campaign," Grenier said. "It's still a riding they would be favoured to win, but just the fact that we're actually talking about it, it does seem the New Democrats are concerned over the question of strategic voting in that riding."

Ottawa Centre shift in 2004

Ottawa Centre shifted to the NDP in 2004, after long-time Liberal MP Mac Harb was appointed to the Senate. During that election, NDP candidate Ed Broadbent beat Liberal candidate Richard Mahoney.

Dewar — whose mother, Marion, served as mayor in Ottawa — won the seat for the NDP in 2006 and has repeated that feat in each election since. As part of the so-called orange wave, Dewar won by an unprecedented 52 per cent in 2011.

Ottawa Centre has also raised more donations than any NDP riding in the country, according to a recent Globe and Mail analysis.

Dewar has become an important critic in the shadow cabinet for the official opposition, as well as a strong voice on foreign affairs issues as the Syrian refugee crisis became a pivotal part of the 2015 campaign.

But as the final week of the campaign drew to a close, he has had to focus efforts on securing his seat in Ottawa Centre.

McKenna's strategy 'textbook'

McKenna began her campaign almost 18 months ago — and now she's knocking on some doors a second time to reach out to voters who may be reconsidering the Liberals as an option, she said.

It's a riding with lots of voter engagement: Ottawa Centre had the highest advance polls turnout in the country last week, with nearly 19,000 of the riding's almost 90,000 eligible voters casting an early ballot.

Ms. McKenna has run an excellent campaign, just textbook. Some day we'll be studying this in university. - Green Party candidate Tom Milroy

There have been no fewer than 10 debates, along with seven candidates registered with Elections Canada.

Conservative candidate Damian Konstantinakos is running in his second campaign. The Conservatives consistently get around 20 per cent of the vote.

Konstantinakos refused an interview request with CBC News.

Green Party candidate Tom Milroy said he hopes to improve upon the five per cent the party got in 2011, but said the push for strategic voting could hurt his count.

"I do think it's going to narrow down to a very very tight race," he said.

"I think for the longest time it appeared that Mr. Dewar was running away with the riding but I know Ms. McKenna has run an excellent campaign, just textbook. Some day we'll be studying this in university."