After electing its first MP on Vancouver Island in 2011, this week's provincial byelection upset in Prince Edward Island suggests the Green Party might want to look east for its next major breakthrough.

The P.E.I. Greens secured their second seat in that province's legislature on Monday when Hannah Bell won a byelection vote in Charlottetown–Parkdale. It brought the number of Green MLAs throughout the country to six, adding to the one MLA the party has in New Brunswick and the three Green MLAs that hold the balance of power in British Columbia.

The elections of provincial party leaders David Coon in New Brunswick in 2014 and Peter Bevan-Baker in P.E.I. in 2015 indicated that the Greens had some potential in the Maritimes. But the federal Greens were unable to capitalize on these gains in the 2015 federal election, when once again only Green Leader Elizabeth May won her seat.

The party's share of the vote slipped to just 3.4 per cent, its worst result since before the party first ran a full slate of candidates in the 2004 election.

But the addition of Bell to the party's roster of MLAs in the Maritimes — the Greens have very little support in Newfoundland and Labrador, and no active provincial party there — suggests the region might provide the party with an opportunity for another breakthrough in 2019.

P.E.I. has shown particular potential for the Greens since 2015. Bevan-Baker is the Island's most popular politician. The latest Corporate Research Associates poll indicates that 37 per cent of Islanders think he would be the best person to be premier — more than the 26 per cent who prefer the current occupant of that position, Liberal Premier Wade MacLauchlan.

Polls show P.E.I. Green Leader Peter Bevan-Baker is more popular than Liberal Premier Wade MacLauchlan. (Randy McAndrew/CBC)

Though the P.E.I. Greens have seen their popularity slip a little in the polls recently, the party is still registering between 13 and 18 per cent support, above its 10.8 per cent result in 2015.

Bevan-Baker has been able to tap into discontent with the duopoly in the province — only the Liberals and the Tories have ever governed P.E.I., and the NDP has only ever won one seat in general elections held since P.E.I. joined Confederation.

He has also exploited opposition to the government's reversal on electoral reform, after a provincial plebiscite found a majority in favour of a change to proportional representation, but with a level of turnout the Liberal government deemed too low.

With the federal Liberals having abandoned a campaign promise to implement electoral reform, this is a seam May could also try to mine.

Beachhead on Prince Edward Island

But federal Liberal seats will be difficult to topple in P.E.I., even where Bevan-Baker and Bell have established a beachhead.

Liberal MP Wayne Easter placed 53 points ahead of the Green candidate in Malpeque in 2015. Even in the portion of the riding that overlaps with Bevan-Baker's district of Kellys Cross–Cumberland, the federal Greens took just 14 per cent of the vote only five months after Bevan-Baker got 55 per cent of it.

In Charlottetown, Liberal MP Sean Casey was 50.5 points ahead of the federal Green candidate in 2015. In Bell's portion of the riding, the Greens took just seven per cent of the vote.

So a good deal of work needs to be done before the Greens can imagine flipping these federal Liberal seats. There's a big gap between the 3,790 people who cast a ballot in the provincial electoral district of Kellys Cross–Cumberland and the 22,472 who voted in the riding of Malpeque.

Green opportunity in Fredericton?

Conversely, the federal Greens may have better odds in New Brunswick, where the provincial party is considerably weaker.

The federal Greens finished third in Fredericton in 2015, losing to the Liberals' Matt DeCourcey by a margin of 33 points. But in the portion of the riding that belongs to Coon's provincial district of Fredericton South, the Greens finished second with about 20 per cent of the vote — eight points above their performance in the federal riding as a whole.

In fact, outside of B.C. and a riding in Northern Ontario occupied by an MP who had crossed the floor from the NDP, Fredericton was the Greens' best result in the 2015 federal election.

But the provincial Greens are polling at only seven per cent in New Brunswick, matching their performance in the 2014 provincial election. And Coon's popularity in New Brunswick does not match that of Bevan-Baker in P.E.I. The federal party may get less of a boost from its provincial cousin in New Brunswick than in P.E.I.

Still some work to do

The Greens are not yet in a strong position to win ridings like Fredericton, Malpeque and Charlottetown. The party's core strength remains in British Columbia, where the Greens are polling at 12.9 per cent in the CBC Poll Tracker. It is on Vancouver Island where the Greens' second federal seat is still most likely to be won.

But the next-best region of the country for the Greens is Atlantic Canada, where the party is polling at 7.4 per cent — well above its 3.5 per cent result in 2015.

The Greens need to increase that support to somewhere between nine and 11 per cent before a win in the Maritimes becomes more plausible. They will also need Liberal support to dip quite a bit below its current 51.9 per cent.

Federal Green Party Leader Elizabeth May has been the party's sole MP since being elected in Saanich–Gulf Islands in 2011. (Sean Kilpatrick/Canadian Press)

Nevertheless, the provincial Greens in New Brunswick and P.E.I. have laid the groundwork for their federal cousins and have written the playbook for victory: having a strong, respected candidate who can present himself or herself as an alternative to old, traditional politics without necessarily emphasizing an environmentalism that might appeal in B.C. but not on the East Coast.

Every win at the federal and provincial level gives the Greens greater resources, more full-time staffers and a higher profile. It also gives them more people who have experience winning elections. With some luck, and a little help from their friends, the federal Greens might be able to add to that roster in the Maritimes in 2019.