Growing up, Bernie Sanders followed the path of many young American Jews. He went to Hebrew school, was bar mitzvahed and traveled to Israel to work on a kibbutz.

But as an adult, Sanders drifted away from Jewish customs. And as his bid for the White House gains momentum, he has the chance to make history. Not just as the first Jewish president — but as one of the few modern presidents to present himself as not religious.

“I am not actively involved with organized religion,” Sanders said in a recent interview.

Sanders said he believes in God, though not necessarily in a traditional manner.

“I think everyone believes in God in their own ways,” he said. “To me, it means that all of us are connected, all of life is connected, and that we are all tied together.”

Here's the answer to one of the most Googled questions about one of the most Googled candidates. (Osman Malik and Sarah Parnass/The Washington Post)

Sanders’s religious views, which he has rarely discussed, set him apart from the norm in modern American politics, in which voters have come to expect candidates from both parties to hold traditional views about God and to speak about their faith journeys.

Every president since James Madison has made the pilgrimage across Lafayette Square to worship at St. John’s Church at least once, according to the White House Historical Association. Only three presidents, Thomas Jefferson, Abraham Lincoln and Andrew Johnson, have been unaffiliated with a specific religious tradition, according to the Pew Research Center for Religion and Public Life. And President Obama and his predecessors have regularly hosted clergy for White House prayer sessions.

Sanders’s chief rival for the Democratic presidential nomination, Hillary Clinton, emphasized her lifelong affiliation as a Methodist during an exchange Monday with voters in Iowa. Clinton did not mention Sanders, but her words underscored the stark contrast between her more traditional approach and that of her rival.

“I am a person of faith. I am a Christian,” Clinton said. “I am a Methodist. I have been raised Methodist. I feel very grateful for the instructions and support that I have received starting in my family but through my church.”

Reticent on faith

For Sanders, rejecting the formal trappings of religion adds to the unconventional nature of a candidacy that has energized many liberals but could prove problematic in a general election. He is a self-described “democratic socialist” who has refused to shy away from policy positions that would expand government and increase taxes.

Sanders often presents his support for curbing Wall Street banks and ending economic inequality in values-laden terms. He recently described it as “immoral and wrong” that the highest earners in the country own the vast majority of the nation’s wealth.

Even so, Sanders has appeared reluctant to delve into discussions about his faith, prompting many to assume on social media that he is more secular than God-fearing.

When late-night TV host Jimmy Kimmel asked Sanders in October whether be believes in God and if that matters to the American people, the senator seemed to avoid a direct response:

“I am what I am,” he said. “And what I believe in, and what my spirituality is about, is that we’re all in this together.”

Sanders, 74, told The Washington Post that his upbringing as the son of an immigrant father and first-generation American mother in Brooklyn instilled in him a sense of morality found in Judaism and many other faiths.

“I want to be treated with dignity and respect, and I want other people to be treated with dignity and respect,” he said.

“I think it is important that a sense of morality be part of our politics.”

A Jewish upbringing

Sanders’s father, Eli, grew up in a rural village in southern Poland and crossed the Atlantic in 1921, driven by penury rather than prejudice to seek opportunities in Brooklyn, where an older brother had settled. He married the daughter of Polish immigrants and made his living as a paint salesman, finding community among a circle of like-minded relatives and friends.

Bernie Sanders, born in 1941, was raised only blocks from where his second wife, Jane O’Meara, later grew up, but it was culturally distant from her Catholic quarter.

“It wasn’t a question of ‘Are we Jewish?’ ” recalled his older brother, Larry Sanders. “It was just as uncontested as saying you’re an American.”

Almost seven years apart in age, the Sanders boys shared a bedroom in a modest but comfortable apartment. Passover Seders would rotate among neighbors. When their father went to synagogue on Yom Kippur, the boys would sometimes wait outside, listening to the World Series. Bernie Sanders’s bar mitzvah was “a big gathering,” Larry Sanders recalled, at which the adolescent looked younger than his 13 years.

Their Jewish education was “unsophisticated,” Larry Sanders said, grounded in a simple moral code of right and wrong.

“He could read a prayer in Hebrew,” Larry Sanders said, “but not with a great deal of understanding.”

Larry Sanders doesn’t remember Judaic teachings — or even the Holocaust — being a common topic of conversation within the family, although a pall hung over the household after the Red Cross brought news that an uncle in Poland had been shot by the Nazis.

Their parents were ardent New Dealers, said Larry Sanders, who went on to become a Green Party member and county council member in England.

By the time Bernie Sanders graduated from the University of Chicago in 1964 and traveled overseas, he was examining ways in which the rest of the world was implementing socialist strategies, his brother said.

When Sanders and his first wife, who was Jewish, decided in 1968 to settle in Vermont, they joined a flow of urban Jews who resisted the materialism of postwar America, according to Benson Scotch, a former ACLU lawyer who was part of the same migration.

They were looking for something “more open to community,” said Scotch, who said he never expected the young idealist to follow the career path he is now on.

‘The ethical thing to do’

People who have known Sanders over the four decades of his political ascent in Vermont — as a member of the leftist Liberty Union Party, mayor of Burlington, and subsequently as an independent member of the House and the Senate — say Sanders’s central interest has always been politics, not religion.

“I can’t tell you how seldom we talked about religion,” said Stanley “Huck” Gutman, a professor of English at the University of Vermont and Sanders’s former chief of staff. Gutman then described his friend’s moral code in terms of core religious tenets.

“He often talks about ‘the ethical thing to do,’ ” said Gutman, “and his ethics are shaped by a concern for social justice and for other human beings that is part of a Judeo-Christian tradition.”

Larry Sanders sums up his brother’s views this way: “He is quite substantially not religious.”

A vivid illustration of Sanders’s approach came in September, on Rosh Hashanah, the Jewish new year. While many Jews took the day off from work and school to worship, Sanders was campaigning — at Liberty University, the evangelical Christian school in Lynchburg, Va.

In his speech, Sanders sought a religious common ground by alluding to a New Testament passage from the Sermon on the Mount that outlines Jesus’ moral teaching.

“I am motivated by a vision which exists in all of the great religions — in Christianity, in Judaism, in Islam, Buddhism and other religions — and which is so beautifully and clearly stated in Matthew 7:12,” Sanders said. “And it states: ‘So in everything, do to others what you would have them do to you, for this sums up the law and the prophets.’ ”

In the interview with The Post, Sanders sought to explain how his approach to political issues, from climate change to income inequality, is grounded in a moral understanding that transcends religious and political partisanship.

“In terms of climate change, you have people as conservative as the evangelicals, many evangelicals, who understand that you cannot destroy God’s planet. And you have Pope Francis, who as you know, I admire very, very much, talking about this planet and the suicidal direction regarding climate.”

Sanders has also used his family history to draw what he says are important lessons about the dangers of democracy when it is untethered from morality. He recalled during a recent breakfast with reporters how a trip he and his brother took to their father’s ancestral village in Poland reminded him of what happened when elections precipitated the rise of the Nazis, leading to the death of 6 million Jews, including three members of Sanders’s family.

“What I learned as a little kid,” Sanders said, “is that politics is, in fact, very important.”

Playing down his roots

But the man who would succeed America’s first black president, and who is in a neck-and-neck race for the Democratic nomination with a woman who touts her history-making potential as the first female president, has done little to promote his own possible historical achievement.

And many of the country’s most prominent pro-Israel donors have lined up behind Clinton, who has long nurtured close ties with the U.S. Jewish community and showcased her strong support for the Jewish state.

Sanders, in contrast, has emphasized his pro-Israel views less over the course of his political career. In recent days, Clinton’s campaign has attempted to portray Sanders as misguided on Middle East issues.

“When I go to a [Clinton] fundraiser, I feel like I’m going into Rosh Hashanah services,” joked Marc R. Stanley, a Texas lawyer and former chairman of the board of the National Jewish Democratic Council. Stanley has supported Sanders’s Senate campaigns but is backing Clinton this year.

Perhaps most puzzling is Sanders’s reluctance to cement cultural connections with fellow Jews by sharing stories from his past — among them which kibbutz he stayed on in the early 1960s.

In Israel, the Kibbutz Movement — the umbrella organization for the 250 communal settlements — launched a Facebook campaign to find out, featuring a Photoshopped picture of the presidential candidate wearing a symbolic Israeli “tembel” hat. After Naomi Zeveloff published an article in the Forward about the search, readers wrote in, wondering why Sanders wasn’t releasing the information:

“What’s the big deal?” they asked. “That’s my question as well,” Zeveloff said.