A strong election showing Monday by third parties that once struggled for slivers of Prince Edward Island's vote is a warning to Tories and Liberals that generations-old political loyalties are fading, say political commentators.

History professor Ian Dowbiggin of the University of Prince Edward Island says the gains made by the NDP and the Green party, which each won about 11 per cent of the popular vote, represents a historic shift that won't be easily erased.

"When you get over 20 per cent of the total number of votes, it's got to reflect a changing of political allegiance, especially among young people," he says.

"The people who were voting yesterday for the Greens and the NDP weren't simply old hippies with pony tails voting their heart."

The Liberals won their third straight majority under rookie premier Wade MacLauchlan, dropping from 20 seats to 18, while the Tories took eight seats and the Green party claimed its first seat in the legislature.

Dowbiggin says the Liberal win shows the electorate is comfortable with the former university president, the province's first openly gay premier.

He also says the Greens and NDP still face huge obstacles in fundraising, candidate recruitment and a first-past-the-post system that works against parties that don't have a strong chance of forming government.

But the old days of predictable swings of the majority of the 27 ridings on the Island from one major party to the other after two to three terms in power are being challenged.

The NDP's share of the vote shot from 3.2 per cent in 2011, when they seldom attracted more than 200 voters in most ridings, to almost winning a Charlottetown seat and quadrupling their overall support.

Green leader Peter Bevan-Brown swept to victory in the riding of Kellys Cross-Cumberland, with his own total of 2,077 votes equalling two thirds of what the entire party was able to muster in the last election.

Don Desserud, a professor of political science at the University of Prince Edward Island, said he's cautious about concluding the results will lead to further growth -- but he was nonetheless impressed.

"It could be a step towards a historic change. What it shows is that there's a substantial number of voters on the Island who do two things: they don't vote for the Liberals and the Conservatives, and they do vote," he said.

Both Desserud and Dowbiggin say interest in the third parties may help explain an overall turnout of 86 per cent of voters, up significantly from the 76.5 per cent turnout in the last election.

Chief electoral officer Gary McLeod says in an email he's unable to confirm the reasons for the increase at this time.

Dowbiggin says the results also demonstrated the failure of the Tories to capitalize on public disenchantment with the government of former Liberal premier Robert Ghiz.

He says many voters identified the Liberals with the provincial nominee program, which brought immigrants into the province if they invested in Island companies. In 2009, the auditor general released a report on conflict of interests that were related to the program.

The professor says that issue, along with provincial financial woes, could have led to a breakthrough for Conservative Leader Rob Lantz.

Instead the party's overall popular vote fell, and Lantz was unable to win his seat in Charlottetown. Dowbiggin said he doubts Lantz can stay on as leader of the party if he can't win a seat in a byelection.