After 10 months of standing outside the House of Commons, NDP Leader Jagmeet Singh has finally decided to try to take a seat.

Singh is expected to announce today that he'll be running in the upcoming byelection in the British Columbia riding of Burnaby South, which will be officially vacated in September when NDP MP Kennedy Stewart steps aside to mount his bid for the mayor's office in Vancouver.

It won't be a cakewalk for Singh. The byelection itself has yet to be scheduled; it must be called within six months of Stewart officially vacating the seat.

The Liberals could bundle the vote with ones that must be held to fill vacancies in the Quebec riding of Outremont — vacated by Tom Mulcair, Singh's predecessor — and the Ontario riding of Leeds–Grenville–Thousand Islands and Rideau Lakes, left vacant by the death of Conservative MP Gord Brown in May.

A byelection campaign in Leeds–Grenville–Thousand Islands and Rideau Lakes must begin by Oct. 30. But a provincial election in Quebec on Oct. 1, and municipal elections in B.C. on Oct. 20, limit the Liberals' options in choosing a date.

NDP Leader Jagmeet Singh toured George Third & Son Steel Fabricators and Erectors in Burnaby, B.C. in March. (Darryl Dyck/Canadian Press)

Singh's decision to run comes after nearly a year of expressing his comfort at being without a seat. He also has said that he'd prefer to run in a riding where he has a personal connection. While Singh has suggested that ridings in Windsor, Toronto and Brampton met that condition, Burnaby was never on the list.

But there's a practical limit on Singh's choices. Of the seven ridings that have held byelections since he took over the NDP — and those where byelections are pending — Burnaby South is the first to fall vacant where the New Democrats have a realistic shot.

NDP history of narrow victories in Burnaby South

Located east of Vancouver, Burnaby South and its predecessor ridings have voted for the NDP in five consecutive federal elections beginning in 2004. Since 1972, at least a portion of the current riding has voted for the New Democrats.

Using the current electoral boundaries — which were redrawn following the 2011 federal election — Burnaby South has been 16.8 percentage points more New Democratic than the country as a whole over the last three elections, ranking 31st on the list of ridings with the steepest NDP 'lean' in the country.

In 2015, Stewart won a narrow victory, taking 35.1 per cent of the vote to 33.9 per cent for Adam Pankratz of the Liberals. Only 547 votes separated the two, while the Conservatives finished a strong third with 27.1 per cent of the vote.

The area that now makes up Burnaby South was similarly split in the past: the NDP won by about two points in 2006, five points in 2008 and four points in 2011, with the Conservatives finishing second in 2008 and 2011.

NDP MP Kennedy Stewart was arrested after joining protesters outside Kinder Morgan's facility in Burnaby, B.C. Stewart is resigning his Burnaby South seat to run for the mayor's office in Vancouver. (Darryl Dyck/Canadian Press)

So Singh could have a close fight on his hands. Polls in B.C. suggest the political climate has only gotten worse for the New Democrats, not better. The party has dropped about four points in the province since 2015.

But Burnaby South's own political climate might be a little friendlier to the NDP's opposition to the expansion of the Trans Mountain pipeline carrying oil from Alberta's oilsands to the B.C. coast. The pipeline's terminal will be in the neighbouring riding of Burnaby North–Seymour. In May, Stewart pleaded guilty to criminal contempt of court relating to his protest against the pipeline expansion.

The Liberals have since purchased the pipeline, making for a clearer political fight between its opponents and the government.

Burnaby South's demographics also might make the riding a good fit for Singh, a practising Sikh and the country's first visible minority leader of a major federal party. According to the 2016 census, just over two-thirds of the riding's population identifies as visible minority and 8.4 per cent is South Asian.

First seatless leader to run in byelection in 16 years

Singh's byelection run for a seat will be the first by the leader of a party represented in Parliament since Stephen Harper ran in a 2002 byelection in Calgary after he became leader of the Canadian Alliance. Though the Liberals and Progressive Conservatives did not put a candidate up against Harper at the time, the NDP did.

Harper previously had been an MP from the Calgary area. Singh, however, previously represented a seat in the Ontario legislature — far from British Columbia.

Stephen Harper was the last major party leader to seek a seat in a byelection when the rookie leader of the Canadian Alliance ran in a 2002 byelection. (Adrian Wyld/Canadian Press)

But there is a long history of Canadian party leaders running for a seat in unfamiliar territory. Brian Mulroney and Jean Chrétien — both Quebecers — ran for seats in in 1983 in 1990 in Nova Scotia and New Brunswick, respectively, when they took over their parties without seats of their own.

The NDP has less of a history of parachuting leaders into byelections. Tommy Douglas, Alexa McDonough and Jack Layton lacked seats when they became leaders of the NDP; all waited until the subsequent general election before putting their names on a ballot.

Singh the second NDP leader to run in Burnaby

Douglas, however, failed to win a seat in the 1962 federal election. One of his MPs stepped aside to create a vacancy for him and Douglas was then elected in a byelection later that year.

Coincidentally, that riding was Burnaby–Coquitlam, which shares some of the same territory as Burnaby South. After winning the byelection (without any "Douglas bump" to speak of in the riding), the former premier of Saskatchewan represented the B.C. seat until he was defeated in 1968.

It's a weighty political legacy for Singh to carry into the Burnaby South byelection. He isn't making it easy for himself. Past leaders in his position generally have contested safe seats in byelections — the leader's party has averaged a 21.7-point margin of victory in the previous federal election in these seats. Stewart won Burnaby South by just 1.2 percentage points.

No leader of a major federal party has tried to secure a seat in a byelection in a riding won by a narrower margin than Burnaby South in 2015. And since 1942 — when Conservative Leader Arthur Meighen left the Senate for an unsuccessful attempt to gain a seat in the House — no leader of a major federal party has suffered personal defeat in a byelection.

That's a winning streak Singh can't afford to break.