Not since the Great Depression disrupted sitting governments across the country has any prime minister presided over a period of such sweeping political turnover as Justin Trudeau has ahead of October's federal election.

Another government could be added to the tally if Dwight Ball's Liberals fail to secure re-election in today's vote in Newfoundland and Labrador — a defeat that would make Trudeau's term in office the bloodiest for an incumbent government in Canadian history.

Trudeau benefited from a widespread desire for change in the October 2015 election. Since then, there have been nine changes of government in the 11 provincial and territorial elections that have been held during the last four years. (Nunavut and the Northwest Territories do not run elections along party lines, and so have been excluded from this analysis.)

Newfoundland and Labrador was the first out of the gate in November 2015, when Ball's Liberals defeated the incumbent Progressive Conservatives. In 2016, Brian Pallister's PCs beat the NDP in Manitoba and Sandy Silver's Liberals defeated the Yukon Party.

In 2017, Christy Clark's B.C. Liberals won the most seats but were replaced by John Horgan's New Democrats with the backing of the B.C. Greens. Last year, Liberal governments in Ontario, New Brunswick and Quebec were replaced by the PCs and François Legault's Coalition Avenir Québec.

Already this year, Rachel Notley's New Democrats fell to Jason Kenney's United Conservatives in Alberta, while Wade MacLauchlan's Liberals were defeated by the PCs under Dennis King in Prince Edward Island.

Only the Saskatchewan Party in 2016 and Stephen McNeil's Nova Scotia Liberals in 2017 have managed to win re-election over the last four years.

An unusual pace of change

So much turnover in such a short period of time is rare. Trudeau's term is only the fourth in Canadian history which saw a majority of provincial elections result in changes of government. The others were those of W.L. Mackenzie King (between 1921 and 1925), Pierre Trudeau (between 1968 and 1972) and R.B. Bennett's single term in power between 1930 and 1935.

Bennett's name is one that Trudeau drops a lot. He has evoked the former Conservative prime minister 19 times in the House of Commons (according to openparliament.ca) to remind the current Conservatives that it was Stephen Harper who had the "lowest growth record" since the market crash of 1929 that sparked the Great Depression.

Harper is the only prime minister whose name Trudeau has uttered more often than Bennett's in the Commons. But Trudeau has his own connection to Bennett — one that does not bode well for his chances in the fall election.

Defeat in the Great Depression

Ten provincial elections were held during Bennett's time as prime minister. Incumbent governments lost eight of them, which was the worst winning record for incumbents in history — until the last four years.

The early 1930s were a time of tremendous political disruption, in Canada and around the world. King's Liberals met defeat in the 1930 election in part because of the turmoil triggered by the market crash of the preceding year.

Newly installed as prime minister, Bennett's popularity quickly dropped as his government failed to grapple with the country's rampant unemployment. When he finally went to the polls in 1935, his party lost more than two-thirds of its seats and King's Liberals were returned to power. The Liberals would stay there for another 22 years.

But Bennett's government wasn't the only one to be sideswiped by the Great Depression.

R.B. Bennett (left) and his Conservatives were defeated by W.L. Mackenzie King's Liberals (right) in the 1935 federal election. (Nelson Quarrington/Canadian Press)

In 1931, the Liberals were defeated in P.E.I., only to be returned to power four years later with every seat in the assembly after the Conservatives failed to do a better job of tackling the upheaval.

In 1933, the Conservatives fell to the Liberals in Nova Scotia and in British Columbia.

The next year, the Liberals' James Gardiner returned to office in Saskatchewan, replacing the coalition government that brought him down after the 1929 election produced a minority legislature. In Ontario, Mitch Hepburn's Liberals beat the Conservatives, who had been in office for the preceding decade.

Before the federal election in 1935 was held, the Liberals saw off the Conservatives in New Brunswick and "Bible Bill" Aberhart's Social Credit, which proposed radical new monetary policies that were later deemed unconstitutional, was swept to power in Alberta. The incumbent United Farmers were shut out of the Alberta legislature entirely.

It was in this context of turmoil and disruption that Bennett met his political end in October of that year.

The lessons from history

There is no clear relationship between change in provincial capitals and change in Ottawa. In cases where an incumbent government has been defeated in the past, about 32 per cent of incumbent provincial governments changed hands prior. The turnover rate at the provincial level has been about 29 per cent at times when federal governments have been re-elected — slightly lower, but not significantly so.

Though Bennett met a catastrophic defeat when the desire for change was sweeping the nation, King won enough seats in 1925 to stay in power with a minority government. In 1972, Pierre Trudeau eked out a slim plurality and also stayed in office at the head of a minority government.

During Prime Minister Pierre Trudeau's first term in office between 1968 and 1972, a majority of incumbent provincial governments were defeated. Trudeau's Liberals were reduced to a minority in the 1972 federal election. R.B. Bennett was prime minister from 1930 to 1935 during the Great Depression, when voters were defeating incumbent provincial governments across the country. (Peter Bregg/Canadian Press)

On the other hand, a number of prime ministers have met defeat after their provincial counterparts were re-elected.

But it might still worry Justin Trudeau that the country is on pace to match the provincial turnover rate of the Bennett years. Bennett was the last prime minister to be elected to office for the first time at the head of a majority government who was subsequently booted out in the next election. Trudeau wants to avoid being the next one.

And as with the Bennett years, parties that share the prime minister's brand are the ones that are suffering most of the defeats. It will be six Liberal governments down if Ball is defeated today, matching Bennett's record.

Of course, Canada's economy is not now in the depths of a Great Depression. Unemployment currently stands at 5.7 per cent, while estimates put unemployment almost as high as 30 per cent during the Depression. But some of the former premiers who have recently become unemployed themselves — Philippe Couillard in Quebec, for example — were canned despite healthy provincial economies.

In short, we appear to be living through a Great Disruption in Canadian politics. It might not be over yet.

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