His party's policies in favour of abortion and same-sex marriage conflicted with Catholic teaching, but many positions Mr. Layton espoused — on social responsibility in the mining industry, peace, environmental issues and care for the poor — were shared by many Catholics and dovetailed with campaigns launched by the Canadian Catholic Organization for Development and Peace and KAIROS.

“The key thing was his constant theme of hope and love,” said NDP MP Joe Comartin, a Catholic who served on the party’s faith and justice committee.

Mr. Layton died from cancer at his Toronto home on Aug. 22. Two days earlier he wrote a letter that friends say captures a deeply spiritual side that grew stronger after he revealed a prostate cancer diagnosis 18 months ago.

“My friends, love is better than anger,” Mr. Layton wrote in the Aug. 20 letter. “Hope is better than fear. Optimism is better than despair. So let us be loving, hopeful and optimistic. And we will change the world.”

Comartin said the letter is “going to be one of those put that in the archives for many generations to come.” He said this message was “not spin” but something Mr. Layton “believed in the core of his being.” And millions of Canadians believed it as well, Comartin said, referring to the last federal election where the New Democrats under Mr. Layton became the Official Opposition for the first time in history.

In a message of condolence Aug. 22, the president of the Canadian Conference of Catholic Bishops, Saint-Jérôme Bishop Pierre Morissette, described Mr. Layton as “a dedicated politician who served his country with devotion and generosity, was concerned for the common good and gave a wonderful example of courage and hope, especially during recent months when struggling against cancer.”

Canadians got a deeper glimpse of Mr. Layton’s spiritual side at the 2010 Canadian National Parliamentary Prayer Breakfast when he spoke movingly of experiencing “this incredible sense of joy” after publicly revealing his battle with prostate cancer.

“I recall him saying something to the effect of not being overtly religious but humbled by the overwhelming number of people who called, wrote or told him personally they were praying for him,” said Toronto archdiocese communications director Neil MacCarthy, who attended the breakfast.

Comartin recalls Mr. Layton telling him how much solace and inspiration he received from this outpouring of prayerful support. Mr. Layton said he wanted to sit down with him and MP Tony Martin, also Catholic, to “spend more time talking about our faith lives.” He regrets now the meeting never took place.

Comartin said Mr. Layton had always believed in a divinity, but “he really never explored it to any significant degree” until after the prayers prompted him to do so.

Martin described Mr. Layton as a man of integrity. He traces Layton’s spiritual roots to his upbringing in the United Church and involvement in church youth activities in Montreal. He swam on the YMCA swim team and was deeply influenced by the activism rooted in the social Gospel, Martin said.

“The whole social Gospel thing permeated everything that he did,” Martin said.

Salt + Light Media Foundation CEO Fr. Thomas Rosica recalls the “good will” Mr. Layton showed toward World Youth Day in Toronto in 2002

"I always found him to be a kind gentleman in his dealings with others,” Rosica said. “He listened attentively to others, especially those who had differing opinions, and showed much respect for people."

Toronto Archbishop Thomas Collins said in a statement: "Our thoughts and prayers are with Jack Layton's family during this most difficult time."  

Prime Minister Stephen Harper called Mr. Layton a friend and praised his “dedication to public life”.

“We have lost an engaging personality, and a man of strong principle,” Harper said.

Catholic Civil Rights League executive director Joanne McGarry said she appreciated Mr. Layton’s forthrightness on public policy issues even though he and his party took positions on abortion and on marriage “that are not compatible with Catholic teaching.” She praised his leadership on other issues, such as aid to seniors and health care. “He is a voice that will be missed.”

Campaign Life Coalition president Jim Hughes called Mr. Layton a "formidable opponent.”  

“In the pro-life battle, he was a very interesting character,” Hughes said.  

When Hughes became active in the pro-life movement 30 years ago, Mr. Layton’s father Robert Layton was a pro-life Progressive Conservative MP. Hughes said he was disappointed Jack Layton failed to follow in his father’s footsteps. The NDP once attracted many pro-life Catholics as did the Liberal Party, Hughes said, but both parties have “strayed from their roots.”