Canadian politics was turned upside down in the last decade when the Liberal party lost its bedrock of support among Catholics.
In 2000, nearly 55 per cent of Catholics voted Liberal, according to the Canadian Election Study. The Catholic vote was a critical ingredient to Liberal success, as it had been for much of the Liberal party's long history in Canada. But by 2008 the Liberals had slipped behind the Conservatives among this critical group.
The next time around, in 2011, "the propensity for Catholics to vote Liberal, already weak in 2008, vanished completely," the Canadian Election Study concluded. That broke a bond ingrained in Canadian politics, one that had been studied and measured as far back as the early 1950s. The Liberal party was simultaneously reduced to a rump.
About 12.8 million Canadians identify as Catholics, making them the largest religious group in the country. A large number live in Quebec, but Catholics inhabit every corner of the country in large numbers. So what drove them away?
On same-sex marriage and abortion, two issues that lingered through the middle of the 2000s, the Liberal party was at odds with official church doctrine. But did that lead voters to switch parties? Or is plummeting support among Catholics a symptom, rather than a cause, of the decline of Liberal Canada?
Sean Simpson of pollster Ipsos-Reid tends to see the relationship as coincidental.
In part that's because the role of religion in Canadian life is shrinking. About half of Catholics told the pollster that religion doesn't play an important role in their lives, Mr. Simpson said. Of the people who identify as Catholic, only 14 per cent actually attend a service every week. Religion will not determine how those people vote, he said.
The real divide is between those who go to a religious service of any denomination – whether at a church or temple or synagogue – and those who do not, Mr. Simpson said.
"It's less about where you go but whether you go," he said.
In 2011, 52 per cent of those who attended a service at least once a week voted Conservative, versus 21 per cent for both the Liberals and NDP, according to Ipsos-Reid. The religious, regardless of their faith, are right up there with the over-65s (53 per cent Tory support) as among the most favourable demographics for Conservatives. Both groups show significantly better results for the Conservatives than their overall total of 40 per cent of the vote.
Protestants and Muslims were more likely than Catholics to say religion played an important role in how they vote (81 per cent of Muslims said so, compared to 64 per cent of Protestants and 50 per cent of Catholics). Protestants and Jews were most likely to vote Conservative (57 and 53 per cent, respectively). Muslims were most likely (52 per cent) to vote Liberal, and least likely to go Conservative (11 per cent), according to Ipsos-Reid.
In 2008, Catholics voted 31 per cent Conservative, 27 per cent Liberal, 21 per cent Bloc Quebecois and 15 per cent NDP, according to Ipsos-Reid exit polling. In 2011, Tory support stayed roughly the same at 32 per cent, while the Liberals dropped further to 19 per cent and the Bloc fell to 12 per cent. The big beneficiary of those shifts was the NDP, which moved up to 35 per cent support among Catholics, according to Ipsos-Reid.
That change demonstrates the extent to which the Catholic vote is a proxy for a party's support in Quebec. About 45 per cent of Canadian Catholics reside in Quebec. The Liberals were badly hurt there by the sponsorship scandal, and are only now under Justin Trudeau showing signs of recovery.
"That story's not finished," Mr. Simpson said. "We'll see if the NDP are as competitive in the next election."
The persistence of the bond between Liberals and Catholics was long a puzzle. Some attributed it to French-English differences or a class divide or the entrenchment of historical voting patterns from an earlier period when religion was more central in public life. What was behind the bond and what broke it is very difficult to say, according to Laura Stephenson, a political scientist at the University of Western Ontario who studied the issue. Trying to chase the Catholic vote would be a difficult strategy to execute, she said.
"It's such an elusive thing that it can't really be chased," Prof. Stephenson said. "Do I think this connection between Liberals and Catholics will come back? I wouldn't put money on it."
Joe Friesen reports on demographics.