The UK has been navigating unchartered electoral territory lately. The Westminster system is vaunted precisely for its predictability of producing an accountable, decisive government. One party is supposed to command a majority, while the other is left to form the Official Opposition. After each parliamentary term, voters can choose to reward the incumbent party or give the opposition a shot. At least, that’s the familiar logic.

A Westminster model of government, however, is at its most effective, and most predictable, in a two-party system. Britain’s two-party system had already been under serious strain for decades, but it was only in 2010 that voters’ abandonment of close ties to the two main parties became much more obvious and consequential.

When the Conservative-Lib Dem coalition was announced, it was difficult to tell to what extent the arrangement reflected a temporary blip or a new reality. If support for the Lib Dems evaporated completely, it is possible that some kind of ‘normality’ would have been restored: the party’s supporters on the left could simply have defected to Labour, while those on the right could have shifted to the Conservatives. Some of this has indeed happened, but not to the extent that the Liberal Democrats will be wiped out. Contrary to the naysayers, the Lib Dems look set to survive their coalition experience. They may lose about half of their seats, but their 20-30 MPs may still prove pivotal in a hung parliament.

The real story of 2015, of course, will be the much-anticipated rise of the Scottish National Party. Labour had hoped that a new leader would give the party time to regroup and win back its once loyal voters in Scotland. But support for the SNP has held firm. Forecast to secure about 50 MPs at Westminster, the SNP’s presence will constitute a much more fundamental challenge to the Westminster system itself than that posed by any other ‘third’ party.

But the road is not entirely unfamiliar; it’s just that Britain hasn’t travelled on it before. Canada’s experience, on the other hand, provides a rough outline for a map. Over the last number of decades, its Westminster model of government has been undermined by the growth of a significant ‘third’ party, in the form of the New Democratic Party (NDP), combined with a complex regional dynamic of electoral competition provided by the Bloc Québecois in Quebec.

With this fragmented party system, it has been routinely more difficult for the largest two parties, the Liberals and the Conservatives, to command a majority in the Canadian House of Commons. As a result, minority governments have been common – almost as common as majority administrations. In its history, eleven minority governments have been formed following a general election. Most of these have been reasonably stable, but they rarely survive a full term.

What could make the UK’s result different on Thursday is the sheer combination of factors at work. In Canada, the Bloc Québecois was at its strongest after the 1993 federal election, when it secured almost all of the seats in Quebec. The SNP’s anticipated victory is, therefore, hardly novel – and nor does it indicate the inevitability of Scottish secession. But at this peak, the Bloc Québecois lacked significant influence in the Canadian Parliament as the Liberal Party managed to command a majority at that time. Thus, even though many Canadians lamented the BQ’s period as the Official Opposition from 1993 to 1997, it has not been in a position to wield pivotal power in Ottawa.

In the UK, in contrast, we are heading for a scenario in which no party is able to command a majority and where the pivotal player is a regionalist-separatist party. This will only add to the complexity and stakes of post-election manoeuvring.

The Canadian experience tells us that the Westminster system, far from perfect, can indeed survive in spite of the consolidation of a multi-party system. Likewise, the forthcoming British experience will not spell the end of the Westminster model of government. Depending on just how ‘pivotal’ the SNP proves to be on Friday, it may feel that way.

Whatever the ultimate outcome, and however the UK’s government is configured after May 7th, the next Parliament will be a fascinating test of just how far Westminster lives up to the model of government to which it gave its name.