Update: Frances Stead Sellers and John Wagner have a great new, in-depth look at Sanders religiosity -- or lack thereof. I encourage everyone to click over and read it, but I also thought it worth resurfacing my look at just how rare a non-religious president would be, from late last year.

Much of the attention paid to Bernie Sanders's presidential campaign has to do with the s-word: Can a socialist be elected president? How much of a socialist is he? What exactly is socialism?

What many haven't picked up on is that a Sanders presidency would be a first in a couple other ways. First, Sanders would be our first Jewish president. And second, while Sanders is culturally Jewish, he has said that he's "not particularly religious" and has been described by some as agnostic.

Asked during an appearance on Jimmy Kimmel's show this week whether he believed in God, Sanders demurred.

"I am who I am," Sanders said. "And what I believe in and what my spirituality is about, is that we're all in this together. That I think it is not a good thing to believe that as human beings we can turn our backs on the suffering of other people."

Sanders added: "This is not Judasim. This is what Pope Francis is talking about -- that we cannot worship just billionaires and the making of more and more money. Life is more than that."

In political terms, this is what's known as a dodge. It's an economic and cultural vision that Sanders attempts to shoehorn into a religious conversation by noting that religious people like Pope Francis feel the same way. It's basically saying, 'I'd rather talk about poor people than God.

Part of this is likely because Sanders has over the decades not spoken often about his Judaism or what he believes or practices, according to profiles of him. Now the highly private Sanders seems to be opening the window a bit as a presidential candidate, if only to make the case that his drive for economic justice is deeply rooted in his philosophical DNA, and is even tribal.
This week Sanders gave some of his most detailed comments about the impact of his faith, telling the New Yorker that two aspects of his lower-middle-class, World War II-era upbringing “exerted a lasting influence.” One was never having much money.
“And the other was growing up Jewish — less for the religious content than for the sense it imbued in him that politics mattered,” the New Yorker reported.
“Sanders told me that, in the aftermath of the Second World War, his family ‘got a call in the middle of the night about some relative of my father’s, who was in a displaced-persons camp in Europe someplace.’ Sanders learned that many of his father’s other relatives had perished. Sanders’s parents had been fundamentally apolitical, but he took away a lesson: ‘An election in 1932 ended up killing fifty million people around the world,’” the New Yorker piece said.
“Let me take a moment, or a few moments, to tell you what motivates me in the work that I do as a public servant, as a senator from the state of Vermont. And let me tell you that it goes without saying, I am far, far from being a perfect human being, but I am motivated by a vision, which exists in all of the great religions, in Christianity, in Judaism, in Islam and Buddhism and other religions."

While Sanders didn't tell Kimmel whether he believes in God, he did obliquely refer last month to his "belief in God."

"I believe that there is a connection between all living things, and that my belief in God requires me to do all that I can to follow the 'Golden Rule,' to do unto others and as I would have them do unto me," he said, according to USA Today.

This appears to be the closest he's come to outlining whatever religiosity he claims.

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)

It's worth noting here that religious definitions are malleable. And it's impossible to know what someone's true beliefs are, beyond what they say. Skepticism about a president's declared religious beliefs has hardly been limited to the many Americans who believe President Obama is secretly a Muslim. Some presidents who have claimed the Christian faith have been suspected of not actually being religious.

An agnostic is defined by Merriam-Webster as "a person who does not have a definite belief about whether God exists or not." These people are often lumped in with atheists, who believe "that there is no deity."

We have never had a president who publicly subscribed publicly to atheism or agnosticism. According to data collected by Pew, two U.S. presidents have been religiously unaffiliated. Both, however, spoke more openly about their belief in God. From Pew's write-up earlier this year:

Two of the most famous presidents in American history had no formal religious affiliation. The first, Thomas Jefferson, lost his faith in orthodox Christianity at an early age, but continued to believe in an impersonal God as the creator of the universe. Jefferson famously edited the New Testament by removing references to the miracles and leaving in Jesus’ teachings.
The second, Abraham Lincoln, was raised in a religious household and spoke frequently about God (particularly as president), but never joined a church. Scholars have long debated Lincoln’s beliefs, including the question of whether or not he was a Christian, and some aspects of his faith remain a mystery.

Much like his economic and political philosophy, Sanders's religion -- or lack thereof -- makes him highly unusual in American history.

Correction: This post has been updated to reflect that Sanders did reference a belief in God in September.