Vancouver Island has been considered a New Democratic stronghold for more than a decade, but the region has taken on a new significance ahead of next week's election: It represents the Green Party's best chances for a breakthrough while also posing one of the greatest threats to the NDP's ambitions to govern.

That dynamic has prompted the leaders of the province's three major parties to campaign on the Island in the dying days of the election, as the Liberals look to capitalize on potential vote splitting on the left and the NDP fight to hold onto seats that would have traditionally been considered safe.

Of the Island's 14 ridings, the NDP went into the current campaign with 11 of them and the Liberals, two.

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Green Leader Andrew Weaver picked up his party's first seat in the 2013 election – unseating a Liberal cabinet minister – and in at least two other ridings drew more than 30 per cent of the vote. Those include Saanich-North, where the NDP, Liberals and Greens came within 379 votes of each other. The Island also gave the Greens their first seat in Ottawa when, in 2011, federal Leader Elizabeth May won in Saanich-Gulf Islands.

"If the Greens are going to have any impact, it will be here," said Norman Ruff, an associate professor emeritus at the University of Victoria, who has watched elections play out since moving to the Island in 1969.

Recent polling has suggested the Greens have increased their backing from 2013, with several putting their support across the Island above 30 per cent – in some cases, ahead of the NDP. Any seat the Greens steal from the NDP, or where the Greens bleed off enough votes for the Liberals to win otherwise close races, is one more the New Democrats must make up elsewhere.

Pollster Greg Lyle said in an e-mail exchange that party strength varies across the island, with the Liberals strong north of the Malahat and the Green's strength in the Capital region. Mr. Lyle said this creates a challenge for the NDP, forcing an almost perfect run of Lower Mainland swing seats to win the election.

His latest poll put the NDP, Liberals and Greens in a statistical three-way tie on the Island.

"The Island is small, but because the race is tight [it] may determine whether it is a Liberal or NDP government and, if it is an NDP government, whether it is a majority or minority," Mr. Lyle wrote. "So Island voters could be the King/Queen makers."

NDP Leader John Horgan was in the mid-Island city of Nanaimo on Friday. While he recalled that the party "painted the Island orange" four years ago, he made a direct appeal to Green supporters to rally around his party to oust the BC Liberals.

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"We need to come together," said Mr. Horgan, who spent Friday campaigning throughout the Island.

Underscoring the stakes, Mr. Weaver turned up at the event within an hour to argue voters should ignore such appeals – which he said were based on fear – and make their own decisions.

"We should be calling on voters to vote no matter who they vote for," said Mr. Weaver, who happened to be campaigning in the area and wanted to offer his views on the NDP appeal.

Beyond that, he acknowledged Vancouver Island is important to the BC Greens.

"Vancouver Island is the Island that elected the first BC Green MLA," Mr. Weaver said. "We know we can win in quite a number of ridings on this Island."

The Liberals have been highlighting an Island-focused platform that promises a new tax deduction for people who rely on ferries, support for a Victoria bid for the 2022 Commonwealth Games and a new salmon research centre in Campbell River.

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Earlier this week, Liberal Leader Christy Clark was looking for a fresh start in the area, brashly touting candidates from southern Vancouver Island.

"It has been far too long that the NDP have taken Vancouver Island for granted," Ms. Clark told a rally at a brewery. "We are going to end that on May 9."

Steve Housser, who is running for the Liberals in Cowichan Valley, said Vancouver Island is a "sea of orange" linked to the resource-based history of the island, creating a tradition of unionized labour more aligned with the NDP.

"Families for years have voted NDP. It's in their DNA." However, Mr. Housser said he was taking hope from the changing dynamics of the Island, with new residents moving there and bringing new perspectives. "The Cowichan Valley, my area, is a whole new population."