A Green party will form the official opposition for the first time in Canadian history, following a closely watched election in the province of Prince Edward Island. The unprecedented result signifies a major milestone for the environmentally oriented political party.

Following weeks of vigorous campaigning in Canada’s smallest province, the Progressive Conservatives (PC) emerged victorious on Tuesday evening with a thin lead in the province’s legislative seats.

With most votes counted, the PC party, led by former journalist Dennis King, appeared to have won 12 of 27 seats.

“All I can say is – welcome to a new day in Prince Edward Island,” King told cheering supporters.

However, much of the focus of election night was on Peter Bevan-Baker, leader of the insurgent Green party. His party appeared poised to take nine seats – a significant increase from the two seats it held when the election was called.

“Islanders responded … by granting us a record number of seats – by far the most seats ever by a Green party in Canada,” said Bevan-Baker, later adding: “My god, I love this island.”

A Scottish-born dentist, Bevan-Baker ran on a fiscally conservative but socially progressive platform in the agriculture-rich province that is on the front lines of a changing climate.

The defeated Liberal government lost most of its seats, finished in third place. Incumbent premier Wade MacLauchlan was unable to hold his seat. “It’s something that happens in politics,” he said following the loss. “The tide has changed.”

King’s minority government will mark the the first time the island’s legislative assembly has been without a majority since the 1800s.

Prince Edward Island Green leader Peter Bevan-Baker. Photograph: John Morris/The Canadian Press/PA Images

While the result fell short of hopes the Green party could form its first ever provincial government in Canada, the result marked significant gains for Bevan-Baker’s party.

The result marks not only a new era in the province’s politics, but also a seismic shift from the two-party system – made up of the Liberals and Progressive Conservatives – that has dominated the island’s politics for the past five decades. Each party typically serves three terms before being replaced by the opposition.

Also on the ballot on Tuesday evening was electoral reform, with a proposal to swap the current first-past-the-post electoral system with a mixed member proportional voting system. The measure failed to reach the required 60% threshold, making it unlikely the new government would implement the results.

Voting was delayed on Tuesday, after a bomb threat was called in at the Assumption parish centre. Federal police closed the voting station and cordoned off the area until it reopened two hours later.

Tragedy also struck the island last Friday, when Green candidate Josh Underhay and his son were killed in a canoeing accident. All parties announced campaigning would be suspended over the Easter long weekend.

Election officials have not yet said when they will hold an election for District 9, where Underhay was listed as a candidate. Election officials even considered postponing the election, given the tight-knit nature of the island – but rules prevented a delay.