While voters in democracies usually only incrementally change the party that they support relative to a prior election, every now and then, a party will go from being a leading or majority party, to holding only a small part of the legislature in a single election.
How many times has this happened in established democracies since World War I and what circumstances caused this to happen?
The Spanish Union de Centro Democrático(UCD) went from:
1979: 6,268,593 votes(34.8%), 168 (out of 350) seats in Congress and 118 (out of 208) seats in the Senate, to
1982: 1,425,093 votes(6.8%), 11 (out of 350) seats in Congress and 4 (out of 208) seats in the Senate.
Now, the causes were complex:
The previous dictator, Francisco Franco, died in 1976. Then Juan Carlos I became Head of State, and he chose as Prime Minister one of the more liberal members of the old regime, Adolfo Suárez. Adolfo Suárez was to begin converstation with the -then illegal- political parties and begin a democratic process.
After forty years of dictatorship, the political landscape was far from settled, there was the official party of the dictatorship (the Falange), and the traditional -but again, illegal- Socialist and Communist parties, and nationalist parties and little else.
So, around Adolfo Suárez the UCD was created. From the beginning it was an odd mix; from people with the same ideas than Suárez, people who just joined to the PM party1, people who joined due to lack of a better option, people who feared the risk of a socialist/communist government. Add to that the economical, social and political instability (new Constitution, legalization of parties -including the Communist Party-, feared and actual coup d´état by the military) and well, the situation was pretty confusing.
But in 1982 some things changed:
The feared coup d'état had happened 23 February 1981 and was defeated, only a minor part of the Army had been part and the conspirators were jailed. The risk of new coups was greatly reduced.
New parties appeared to the right of the political spectrum, most importantly Alianza Popular (AP), leaded by one of Franco's ex-ministers, Manuel Fraga.
With a scenario still far from perfect, buy way more stable, the ideological differences within the UCD caused it to dissolve. Many groups from the UCD left it, mostly joining Alianza Popular or nationalist parties.
The Socialist Party (PSOE) moderated its line, renouncing to Marxism.
The political infighting and divisions in UCD, the split of part of the conservative vote that went to AP and the moderation of the PSOE that made it more palatable to the moderate electors ended with the ascent of the PSOE2 and the sinking of UCD.
UPDATE Looking for something else I just found a more extreme example, the Romanian National Salvation Front. Again, a case of a "national unity" party that skyrocketed in time of crisis (the ousting of Nicolau Ceacescu) only to suffer due to splits shortly after.
Presidential Candidate (Ion Iliescu): 12,232,498 votes, 85.1%.
Senate: 9,353,006, 67.02%, 91 seats out of 119.
Assembly of Deputies: 9,089,659, 66.31%, 263 seats out of 395.
No Presidential Candidate.
Senate: 1,139,033, 10.38%, 18 seats out of 143.
Assembly of Deputies: 1,108,500, 10.19%, 43 seats out of 341.
1Forty years of dictatorship have a deep impact in how people behave.
2That in 1982 got 10,127,392 (48.11%) votes, with 202 (of 350) seats in Congress.
Party Composition of Congress, 1855-2017
It's not in your time frame, but the US election of 1860 eliminated the Whig party and marked the real start of the Republican party. More relevantly, this built to a Republican domination after the 1928 election, controlling House, Senate, and the presidency. The 1930 election did not change control of anything (no presidential election). The 1932 election flipped control of all three. Except for four years in the 1947-55 period, the Democrats controlled the House from 1932 to 1994.
The 1946 election might meet your criteria in the House. A solid advantage by the Democrats turned to a similar advantage by the Republicans.
Republicans did a bit better in the Senate, and starting in 1952, much better in the presidency. But it wasn't until 1994 that they recovered control of the House. Control then flipped in 2006 and back in 2010.
The Senate did not move as distinctly as the House. Its nature is that it takes three elections before every member has faced the voters. While control can shift in a single election, it tends to do so in smaller increments than in the House. And of course the presidency can only change every other election. This makes the US inherently less subject to big flips in controls, although the House can flip quickly.
I'll try to answer your question with regards to Canada.
Canada has a constitution that splits jurisdiction over matters between the federal government and the provincial governments. Provincial governments are not considered subservient to—nor do they serve at the pleasure of—the federal government (which is why, in Canada, it tends to be more appropriate to call them two orders of government rather than two levels of government). For this reason, I think it is just as important to consider provincial elections as it is federal, but I can only really speak to a few provinces.
First, federal elections. There were a few that stood out to me when I first read your question, but after looking more deeply at the election results it turns out only one really fits your criteria. From Confederation in 1867 until the 1990s, the Conservatives and Liberals essentially went back and forth as governing party and Official Opposition (the second-place party). There was a bit of an anomaly in 1917 when the Conservatives and some Liberals came together to form the Unionist Party (which was essentially an election about conscription), but the Unionist coalition was gone by the next election in 1921 (technically, the Conservatives came third in that election, but they were still named the Official Opposition due to the leader of the second-place party declining Official Opposition status—and so the largely two-party state continued). In 1945, the Conservatives were renamed the Progressive Conservatives. The two parties would continue to go back and forth.
In 1984, the Progressive Conservatives came to power by winning more seats than any party had/has in any other election before or since. However, the Liberals (whom the PCs replaced in that year) clung to second place and didn't go away. For that reason, I don't think this election qualifies for your criteria.
The election in 1993 was the one that definitely qualifies. The formation of two new parties—the Bloc Québecois and Reform—resulted in a huge collapse of the Progressive Conservatives, who went from 169 seats in the prior election to only 2. There were two major reasons for the collapse:
The Progressive Conservatives would never play a major role in federal politics again, eventually merging with the Reform Party (which at this point had been renamed the Canadian Alliance) prior to the 2004 election.
Although it doesn't really qualify by your criteria, if you want to see an interesting blip, check out the 2011 election. The NDP catapulted into the Official Opposition and the Bloc was devastated, reduced to only 4 seats. The NDP saw massive success in Québec, largely replacing the Bloc. The Liberals flailed under leader Michael Ignatieff, with the Liberals dropping to third-party status.
Provincially, the first province to look at is Alberta. Alberta tends to elect dynasties, which eventually die out and are never or rarely seen again. Any party that has ever been in power has never returned to power once it was replaced (and that dates back to 1905 when the province joined Canada).
The Liberals won the first four elections with a majority every time.
In 1921, the UFA (United Farmers of Alberta) replaced the Liberals. There were some scandals, but this change can also be attributed to the Conservatives (the former official opposition party) splitting into two caucuses and spending a lot of time bashing the Liberals. The UFA targeted their campaign in the right way. They would win three elections—all by majority.
In 1935, the Social Credit came to power. The UFA were obliterated, losing all 36 seats (their former majority). They would never be elected to a single seat again. In one of the weirdest stories of political leaders you'll ever read, the Premier was forced to resign as Premier after being found guilty of seducing a secretary. In socially conservative Alberta, that was the nail in the coffin for the UFA. The Liberals, who tried to run on the success of the federal Liberal Party at that time, weren't able to attract much of the vote (although they still formed the Official Opposition with 5 of 63 seats). The Social Credit would win nine elections (all majorities), governing until the early 1970s.
In 1971, the Social Credit had governed for 36 years and were seen as tired and old-fashioned. The Progressive Conservatives had a charismatic leader in Peter Lougheed, who brought the PCs to power on strong victories in the province's two largest cities: Edmonton and Calgary. They would go on to win a total of 12 elections—all majorities—governing until 2015. The Social Credit formed the Official Opposition in 1971, but died off over the next three elections and never won another seat again from 1982 on. (In 2012, the newly-formed Wildrose Party was expected by many to come to power. The PCs were already being viewed as tired and their leader had retired six months prior. However, a few ill-timed comments by some social conservatives lead many Albertans to go with the devil they knew. The PCs lost traction in southern Alberta but maintained support in northern Alberta, Calgary, and Edmonton.)
The 2015 election was interesting. The PCs were now seen as even more tired. After 80 years of right-wing governance, Albertans elected a left-wing party in the NDP (another majority). This election was about change, and the Wild Rose would have likely won if not for the fact that they split the vote with the PCs. A number of high profile Wildrose candidates had crossed the floor to join the PC party—a decision that would end most of their fates in politics. It's hard to know what will come of the Progressive Conservatives (they went from 61 seats in 2012 to 10 in 2015), but it's very possible that the party will merge with the other conservative party—the Wildrose—once a new PC leader is chosen by the party membership this spring.
The other province I can speak to is British Columbia, although I'm going to be more succinct. In 1991, the NDP were elected after 40 years of almost-uninterrupted rule by the Social Credit Party. Other than the seven seats they won in 1991, the Social Credit would never again win another seat. This change was largely due to a shift from fiscal conservatism to social conservatism, with many moderate supporters shifting to the Liberal Party.
After two successful elections, the NDP were destroyed in 2001, dropping from 39 seats (a majority) to only 2. This change can be attributed to a lot of things, but there were two major scandals involving ferries and bribery that top the list. This election doesn't really qualify based on your criteria, however, because the NDP remained the Official Opposition and have ever since (even bouncing back to win 30+ seats in the three most recent elections). There was an expectation that the NDP would take over in the 2013 election, but the Liberals returned to power.
