On Dec. 12, voters in the federal riding of Mississauga-Lakeshore will go to the polls in a byelection called by Prime Minister Justin Trudeau last month. The Greater Toronto Area (GTA) riding has been without representation since last spring when three-term Liberal MP Sven Spengemann suddenly resigned to accept a role with the United Nations.

Mississauga-Lakeshore will be ground zero in the next federal election. It's precisely the sort of suburban, diverse and middle-class riding the Conservatives must win if they’re to dislodge Trudeau’s Liberals after nearly a decade in power. By the same token, the Liberals must win ridings like this one across the GTA if they’re to secure a fourth consecutive mandate.

The stakes could not be higher in what’s been a surprisingly sleepy byelection campaign that has failed to garner national attention.

That’s because the results in Mississauga-Lakeshore on Monday evening could signal what’s to come on the federal political scene as the country looks ahead to an election that could be triggered at any point over the next three years. Which party prevails in this critical swing riding, and by what margin, will be instructive for party strategists as they plot a path forward for their respective parties in yet another precarious minority Parliament.

Byelection results can have little to no impact on national political trends, or they can foreshadow seismic shifts among the electorate. An unexpected byelection result can be illustrative of broader political sentiments across the country — attitudes that even mainstream media may not be attuned to.

There are dozens of byelection results over the decades that foretold nascent mindsets emerging on the ground. Take, for example, the byelection results from another “bellwether” GTA riding from almost a decade ago. In 2014, Whitby-Oshawa suddenly found itself with no representation after the death of its MP, Jim Flaherty, the former federal minister of finance.

At the time, Stephen Harper’s Conservatives led in most public opinion polling, despite approaching a decade in power. The once-dominant Liberal Party was a shell of its former self, reduced to third-party status in the House of Commons, and rookie leader Justin Trudeau was perceived as a lightweight by much of the Canadian establishment. In fact, it was the NDP’s Thomas Mulcair as leader of the Official Opposition who was seen as Harper’s chief opponent.

But when the votes were tallied, Liberal candidate Celina Caesar-Chavannes finished a close second, surprising many observers. It was this strong local showing that foreshadowed Trudeau’s unprecedented, come-from-behind win in 2015 when Liberals swept the GTA, easily winning Whitby-Oshawa — a riding they still hold today.

Just as often, byelection results mean nothing for the winning or losing party. The reality is these hyper-local elections give voters the rare opportunity to signal their frustration with the powers-that-be without being able to defeat the government. This dynamic often leads to poor byelection results for otherwise popular governments, as voters understand the stakes are merely local.

Voters cast their ballots in Monday's federal byelection. The swing riding of Mississauga-Lakeshore will be ground zero in the next federal election, writes @andrewaperez. #cdnpoli

With this in mind, what are the dynamics at play in Mississauga-Lakeshore?

The riding is the textbook definition of a “bellwether” riding that almost always aligns with national or provincial trends. Provincially, the riding has been held by the governing party in every election since 1995. On the federal scene, it was represented by Liberal MPs for 26 of the past 30 years but fell to the Conservatives when Stephen Harper won a majority government in 2011.

Spengemann, its former MP, won the riding by more than 3,500 votes a mere 15 months ago. While national political dynamics have shifted somewhat over the past year as a result of Pierre Poilievre’s populist-inspired rise as Conservative leader, this recent margin of victory must be encouraging for Trudeau’s inner circle.

But that’s not all Trudeau’s Liberals have going for them as Dec. 12 approaches.

Their candidate, veteran politician Charles Sousa, comes to this local fight with a significant profile. As Ontario’s former minister of finance, Sousa comes armed with gravitas and substantial government experience. He’s well-connected in the riding’s Portuguese community and would be an immediate contender for a major cabinet post. Sousa’s prospects are also aided by the fact his party remains statistically tied with the Tories in most recent public opinion polls.

Sousa might be just what Trudeau’s Liberals need as they fight back the “three-term blues” amid an intensifying affordability crisis. Policy aside, the number 1 criticism launched against this government is its poor communications and inability to empathize with the everyday struggles Canadians confront in an increasingly uncertain world.

Sousa could serve as an antidote to some of the government’s challenges. A strong communicator, he’s long been extolled for his deep radio voice. He’s also a talented political organizer that could lend an important hand to the party’s efforts across the seat-rich GTA in the next election campaign. With only Minister of Transport Omar Alghabra representing Mississauga in Trudeau’s inner circle, Ontario’s third-largest municipality could benefit from a second voice at the cabinet table.

While some observers are predicting a significant margin of victory for Sousa on Monday, the race might ultimately be tighter, mirroring the national mood. Still, expect the Liberals to prevail due to the strength of Sousa’s personal appeal and the party’s remarkably enduring brand across the GTA.

Come the morning of December 13, the questions aren’t likely to centre around which party won Mississauga-Lakeshore, but on the margin of victory and what it portends for the dynamics at play in the next general election. After winning most Toronto-area ridings by wide margins over the past three elections, a photo-finish win for the Liberals could signal they’re losing ground across the seat-rich Greater Toronto Area. In the same vein, a clear loss for the Conservatives could foreshadow future challenges for the party in a region that traditionally determines which party forms government in this country.

Andrew Perez is a Toronto-based public affairs strategist, freelance writer, and political activist and commentator. He works as a senior consultant in the Toronto office of Hill+Knowlton Strategies.

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