The biggest take-away from the four federal by-elections held on Monday has nothing to do with Stephen Harper's Conservatives.
Yes, they took a hit, but in the grand scheme of things, the fact that they hung on to two seats in the face of a simmering Senate scandal ranks as a small victory. Their government's majority is safe. The by-elections had absolutely no impact on the balance of power in the House of Commons.
Where they do matter is what they reveal about changing dynamics on the opposition side – a contest pitting Justin Trudeau's Liberals against Thomas Mulcair's New Democrats.
The Liberals showed a surprising surge, retaining their seats in Bourassa and Toronto Centre and placing second in the Manitoba ridings of Provencher and Brandon-Souris – where they had sunk to third and fourth places, respectively, in the 2011 federal election.
In Brandon-Souris, they came awfully close (about 400 votes) to scoring an upset: "Just want to point out that you're all up past midnight wondering if #LPC will beat #CPC in rural Manitoba. I'd call that progress," Gerald Butts, Mr. Trudeau's senior adviser, tweeted.
He's right. In the space of two years, the Liberals have transformed themselves from a decimated, directionless party into Ottawa's equivalent of the comeback kid.
The NDP, in contrast, failed to build on the momentum that catapulted them to Official Opposition status in 2011. Sure, the party vote held steady above 30 per cent in Bourassa, and it boasted its best showing yet in Toronto Centre. But both of those results gained them exactly zero seats. And in Brandon-Souris and Provencher, the NDP's vote share buckled. Has the Orange Wave crested?
In politics, by-elections are the equivalent of pre-season games. The stakes aren't high, but the results are a litmus test, telling us about what to expect in the upcoming season.
The next federal election is still a long way off. Neither Mr. Trudeau nor Mr. Mulcair have been tested in a general election.
But now, there is a new calculus at play. The Liberals are back from their near-death experience. The New Democrats are under pressure. And the Conservatives should consider themselves warned.