Once it was western alienation. Now it's western regeneration.

Western Canada is in the midst of a significant changeover in its politics as Saskatchewan Premier Brad Wall, Canada's longest-serving premier, makes room for someone else.

Wall said Thursday renewal would be good for his province and his party. He has led Saskatchewan since 2007 and the Saskatchewan Party since 2004. But Wall is far from the only political leader in Western Canada about to be replaced

The parties that form the Official Opposition in all four western provinces are in the midst of leadership races.

Christy Clark stepped down as B.C. Liberal leader last month after her minority government was defeated by the NDP.

In Alberta, the Wildrose and Progressive Conservative parties merged to form the United Conservative Party (UCP). Among those vying for the new party's leadership are former Conservative MPs Brian Jean and Jason Kenney.

New Democrats in Saskatchewan and Manitoba are also looking for new leaders after their defeats in 2016 provincial elections. The Manitoba NDP will choose its next leader in September, while their counterparts in Saskatchewan will make their choice in May.

The Manitoba Liberals, the third party in the province's legislature, are also running a leadership campaign, while the Alberta Liberals chose their new leader, David Khan, in June.

To the centre, right or left?

It all makes for a lot of change coming in the political landscape, with potentially significant shifts in the region's politics.

The B.C. Liberals, a coalition that includes federal Liberals and Conservatives, could choose to go either to the centre — ground the New Democrats, in an alliance of their own with the provincial Greens, may struggle to hold — or to the right in order to differentiate themselves from the new government.

In Alberta, the next leader of the UCP will have a big role in deciding whether it goes to the right, where the Wildrose once stood, or the centre, the traditional territory of the PCs.

Change is in the air in Manitoba, where the front-runner in the NDP leadership race appears to be Wab Kinew, a 35-year-old Indigenous former broadcaster and rapper. The only declared candidate for the Saskatchewan New Democrats is Ryan Meili, who is solidly on the party's left flank.

The outgoing Premier sat down with Hannah Thibedeau to discuss his legacy and his future 7:50

A glittering prize

The prize offered by Wall's departure is glittering. The province isn't scheduled to hold its next election until 2020, giving his replacement potentially more than two years to put his or her stamp on the government and the Saskatchewan Party.

The polls suggest the party may face its toughest election fight in over a decade, but nevertheless the next leader could reasonably expect even odds of re-election in 2020. That means the Saskatchewan New Democrats could be choosing a future premier, too.

The changes about to take place among some of the opposition parties in Western Canada could have repercussions at the national level sooner rather than later. The UCP is well positioned to defeat Rachel Notley's New Democrats in Alberta's scheduled 2019 vote, while the B.C. Liberals could be back in power even earlier than that, depending on the longevity of newly installed Premier John Horgan's minority government.

The Manitoba New Democrats, who were defeated in 2016 after 17 years in office, may have to sit on the opposition benches for some time yet.

Nationally, musical chairs

When the Saskatchewan Party names Wall's replacement, Ontario's Kathleen Wynne will become the dean of the provincial premiers, having been sworn into office in early 2013.

She will be one of the premiers to hold that title with the least seniority in Canadian history.

That is because there has been an unusual amount of change in recent years. After Wall rides off into the prairie sunset, every western province will have had a change at the top since 2015. Newfoundland and Labrador and Prince Edward Island can also be added to that list, while Quebec and New Brunswick changed governments in 2014.

Trudeau loses a critic

Saskatchewan Premier Brad Wall, centre, walks past Prime Minister Justin Trudeau at a First Ministers meeting in Ottawa in November, 2015. Wall and Trudeau clashed over carbon tax policy and the Liberal government's policy on refugees. (Sean Kilpatrick/The Canadian Press)

Prime Minister Justin Trudeau might be glad to see the back of Wall, a fierce critic and the conservative voice with the highest profile nationwide — more Canadians are familiar with him than with Andrew Scheer, the new leader of the federal Conservative Party.

Wall will undoubtedly still voice his opposition for as long as he is in the job — and perhaps after that as well — but that voice will not carry the same weight now that it has an expiration date. His replacement is unlikely to have the same profile for some time, if ever.

A lot of new voices are about to be heard out of Western Canada. Whose will be loudest?