But he offered a rare glimpse into his spiritual views in an interview with The Washington Post published Wednesday.
“I think everyone believes in God in their own ways, “ said Sanders, who polls show is neck-and-neck with Hillary Clinton in Iowa and opening a large lead in New Hampshire. “To me, it means that all of us are connected, all of life is connected, and that we are all tied together.”
Sanders identifies as both Jewish and secular. He said he's not actively involved in any organized religion. If elected, Sanders would become the fourth president in U.S. history to claim no organized religious affiliation. He also would also be the first Jewish president.
Sanders was raised by Jewish parents. He attended Hebrew school as a child and became a bar mitzvah at age 13, as is the custom with Jewish boys old enough to be accountable for their actions. According to Jewish law, Sanders is Jewish, through and through.
Some see his Jewish upbringing in his frequent discussion of ethics and morality.
“He often talks about the ethical thing to do, and his ethics are shaped by a concern for social justice and for other human beings that is part of a Judeo-Christian tradition,” Stanley “Huck” Gutman, Sanders’ former chief of staff, told The Washington Post this month.
During a meeting hosted by the Jewish Federation of Greater Des Moines in Iowa in September, Sanders told the crowd: “Historically, the Jewish people have been strong advocates fighting discrimination and fighting for social and economic justice.”
Sanders also draws from the spiritual teachings of other faiths to support his social justice causes. His wife, Jane, was raised Catholic, and Sanders has found an ideological ally in Pope Francis on issues of the environment, corporate greed and inequality.
In a message posted on Facebook during the pontiff's U.S. visit in September, Sanders explained why the pope's views strike such a chord for him -- and in doing so revealed a glimpse at his own spiritual beliefs.
Pope Francis "is asking us to become a different kind of person, where our happiness and well-being comes from serving others and being part of the human community -- not by spending our lives accumulating more and more wealth and power while oppressing others," Sanders wrote.
He expressed a similar view in his interview with the Post, saying: “I want to be treated with dignity and respect, and I want other people to be treated with dignity and respect."