In theory, that vote heralded the arrival of a new political era. The Liberal Party's day was done — the broadly centrist institution that dominated Canadian politics in the 20th century was no longer fit for purpose. Canada would finally become more like its sister democracies, with a clear contest between a distinct party of the political right and a distinct party of the left. The future seemed to belong to the Conservatives and the NDP.

Then things changed again, as they are wont to do. Foremost among those unforeseen developments was Justin Trudeau's election as Liberal leader, which happened 10 years ago this week.

In the short term, Trudeau's mere presence breathed a bit of new life into the lungs of a prostrate party. In time, it also gave the party a new sense of direction. If the worst thing that could be said about the Liberal Party was that it represented the "mushy middle," the best thing that could be said about Trudeau's early leadership is that he made the party less mushy.

He announced that he would support the legalization of marijuana. He declared that his party would take a strict pro-choice position in favour of abortion rights. He unceremoniously ejected Liberal senators from the party's parliamentary caucus. And then he laid out a party platform that did not include a commitment to balancing the federal budget.

Each of these moves — like Trudeau's own decision to seek the party leadership — was met with some level of consternation and skepticism. But four years after the party was given up for dead, the Liberals won 184 seats and Trudeau became prime minister.

What has taken shape since then is the most active and activist generation of Liberals to hold power since Lester B. Pearson's government in the 1960s.

Justin Trudeau arrives on stage in Montreal on Oct. 20, 2015, after the Liberals won the general election. (Nicholas Kamm/AFP/Getty Images)

In 2011, when Michael Ignatieff was leading the Liberals, the party platform outlined $8.2 billion in new investments spread over two years. In 2015, Trudeau's platform covered $149.8 billion over four years. The words "racism,""gender" and "reconciliation" don't appear at all in the 2011 platform. Those words appeared 28, 46 and 19 times in the Liberal party's 2021 platform.

Some of those changes in language and emphasis might simply reflect the changing times ("reconciliation" had not really entered the popular lexicon when the Liberal platform was written in 2011). But they also reflect a leader and a party that have tried enthusiastically to speak to emerging demands and issues.

On his 10th anniversary as leader, Trudeau's government may be closer to the end of its time in office than the beginning. Much of the shine has come off the famous son of Pierre Trudeau. But the Liberals remain competitive in public opinion polling and comfortably ahead of the NDP.

Did the prophecies come true?

One way to read the events of the past 10 years is to conclude that the post-2011 theories of realignment turned out to be broadly correct — that the party system did polarize, with the Liberals shifting to become the dominant party of the left.

There may be something to that, at least in the short term. But it's also possible to overstate how much the Liberals have moved leftward. The Liberals remain far less inclined than New Democrats to talk about class or heap scorn upon the rich and powerful.

Despite major new social investments, the Liberals still seem reluctant to create new federally run programs. Dental care is only happening because the NDP demanded it, while Liberal interest in pharmacare has waned.

Liberal Leader Justin Trudeau, left, and NDP Leader Jagmeet Singh prepare for the start of the federal election English-language leaders' debate in Gatineau, Que., on Sept. 9, 2021. (Justin Tang/The Canadian Press)

Even when you consider trends in federal spending, the Liberals' leftward lurch seems more like a nudge. As a share of GDP, federal program spending in 2023-24 is projected to be merely on par with what it was in the late 1980s, when Brian Mulroney's Progressive Conservative government was in office.

In electoral terms, it's also possible to conclude that Trudeau's election victories have merely dressed up what is actually a long-term decline in the Liberal Party's standing.

The ceiling on Liberal support does seem to have been dropping gradually since Mackenzie King's Liberals received 51.3 per cent of the vote in 1940. Louis St. Laurent topped out at 49.2 per cent, Pierre Trudeau at 45.4 per cent, Jean Chrétien at 41.2 per cent. While Trudeau won a majority in 2015, the Liberals could only draw 39.5 per cent of the vote.

If the ceiling falls any further, it will be hard for a future Liberal leader to stand up.

But the same is broadly true of the Conservative Party — a party that has its own existential challenges. John Diefenbaker's Progressive Conservatives won 53.6 per cent of the vote in 1958 and Mulroney got 50 per cent in 1984. Stephen Harper's Conservatives couldn't get more than 39.6 per cent.

In a system that includes both a durable NDP and a resilient Bloc Québécois (and a Green Party of some sort), it might simply be very difficult for any party to routinely capture much more than 40 per cent of the vote.

So the Liberals probably won't be able to dominate this century like they did the last one (from 1896 to 2006, the Liberals governed for 80 years). When they do govern, they might have to work more often with other parties (as they are now).

Not mushy enough?

Ten years after Trudeau became the 13th leader of the Liberal Party of Canada, there is a new complaint — that the party is now not mushy enough.

Political polarization is worth worrying about. Taken to extremes, it can breed the sort of tribalism that makes a democracy difficult to manage. And it's very possible that the next Liberal leader will decide that Trudeau took the party too far to the left. Economic or political circumstances might require the Liberal Party to shift — just as it has in the past.

It's also possible that the political centre isn't, or wasn't, quite where it was thought to be. And while some pundits might prefer moderation, other Canadians might fairly want progress to happen faster than a more centrist approach would allow.

Any Liberal who aspires to win elections might also note that while the Liberal vote has eroded, the combined Liberal-NDP vote has consistently hovered around 50 per cent for the last 40 years — peaking at 59.2 per cent in 2015 and only once dropping below 46 per cent (in 2008). And on an issue as central as climate change, Conservative voters are much less enthusiastic about government action.

But the ultimate lesson of the 2011 election and the last 10 years is that the future is very hard to predict — and that political success depends on both a little bit of luck and an ability to adapt.