In 2015, the Liberals swept Atlantic Canada, winning every federal seat and forming government in every provincial capital. Now, the Liberals are in a neck-and-neck fight with the Conservatives in the polls and two of the four Liberal premiers in the region have been replaced by Tories.

A third will see his fate decided in Thursday's provincial election in Newfoundland and Labrador.

So what are the factors leading to this shift in Atlantic Canada and how might it play out in October's federal election?

Atlantic Canada was the Liberals' strongest region in 2015. The party captured all 32 of Atlantic Canada's seats and won the popular vote by a margin of 40 percentage points over the Conservatives.

Prince Edward Island, Nova Scotia and New Brunswick all had provincial Liberal governments when Justin Trudeau became prime minister. Newfoundland and Labrador got one as well after its November 2015 vote.

The CBC Canada Poll Tracker now gives the Liberals just a two-point lead over the Conservatives in Atlantic Canada, putting at risk a dozen or more of the party's seats in the region. Provincial Liberal governments in New Brunswick and P.E.I. have been chased from office and the polls suggest that Dwight Ball could be at risk of losing power in Thursday's provincial election in Newfoundland and Labrador.

If that happens, the last Liberal provincial premier will be Stephen McNeil in Nova Scotia.

On this week's episode of The Pollcast podcast, host and CBC polls analyst Éric Grenier is joined by Robert Ghiz, Liberal premier of P.E.I. from 2007 to 2014, and Tim Powers, Conservative strategist and vice-chairman of Summa Strategies, to break down the region's political landscape.

Listen to the full discussion above — or subscribe to the CBC Pollcast and listen to past episodes of the show.