As for same-sex marriage, Ms. Campbell declared it “a fact of life here.”

She also attributed the unity to the parliamentary system, where the prime minister is enormously powerful and the executive is in the legislative branch. “It’s a different system in the United States. Here, the parties have to come to common ground much more. There’s much more coherence, much more party discipline.”

“The notion that the extreme can dictate the mainstream is very much harder in Canada,” she said. “The problem in the United States is that the extreme can dictate, particularly in the primary process, which tends to have more extreme single-issue groups, where they can actually nominate people who do not represent the mainstream of the party. We don’t have that in Canada.”

In her view, “Canada is in many ways much more tolerant than the United States.” Citing the Canadian researcher Michael Adams, head of Environics and author of “Fire and Ice ,” a 2003 best seller comparing the United States and Canada, she said, “He argued that although the Canadian and U.S. economies have become more integrated, socially we’ve become less alike. Canada has become more socially liberal and less religious than the United States.”

Ms. Campbell — who was prime minister for only four months in 1993, losing her position when the government was defeated in elections that year — can claim other political firsts: first female minister of justice and attorney general, first female minister of national defense and first woman elected leader of the Progressive Conservative Party of Canada.

Every step of the way, she had a hand in efforts to remove social and sexual discrimination. “You try to create a new normal, a new level of acceptance,” she said. But if there’s a single issue that absorbs Ms. Campbell, a consultant on the advancement of women and democracy, it is women’s rights — an area where Canada has a mixed record.

When it comes to gender equality, Canada has 76 women in the elected lower house of Parliament and ranks 40th in the world on the Inter-Parliamentary Union’s 2012 list . The United States has 73 female representatives and 17 female senators and ranks 78th in the world. The United States ranks a notch ahead of Canada — 17 and 18, respectively — in the 2011 World Economic Forum Global Gender Gap Report but lags behind Canada on women’s political empowerment.

The widest gap seems to come in child care. According to the World Economic Forum Global Gender Gap Report, Canada offers longer maternity leave, maternity leave benefits and maternity coverage, paternity leave and paternity leave benefits, and public and private allowances for day care. The United States has no national policy for paid parental leave.

As for women running for office, Ms. Campbell said some people “are uncomfortable having you there. They can’t say it’s because she’s a woman. So they look for reasons. They never give you the benefit of the doubt.” Looking back at her own campaign, she voiced a sentiment common among politicians: “Many Canadians favored me,” she said, “but my biggest problem was the press. I didn’t look or sound like any of the others. It was a very difficult campaign.”