Last week, Bernie Sanders gave a much-touted foreign policy speech at Westminster College in Fulton, Missouri, the same location where Winston Churchill delivered his famous “Iron Curtain” address in 1946. The contents of the speech were intriguing. So was its timing.

Sanders delivered it on the first day of Rosh Hashanah.

This has become a pattern for the Vermont Senator. In 2015, Sanders used the Jewish New Year to deliver a major address on, ironically enough, religion and public life, at Liberty University, an institution founded by Jerry Falwell. In 2016, he spent Yom Kippur at the White House meeting Pope Francis and talking about it on CNN.

It’s a pattern he’d do well to reconsider. Although he considers himself Jewish, Sanders is not, in his words, “actively involved with organized religion.” That is, of course, fine. He can observe or not observe Jewish holidays however he’d like. But he’s also a former — and likely future — contender for the presidency in a deeply religious country. And flaunting his disrespect for his own religious tradition isn’t smart.

In general, Americans are less judgmental about what kind of religion a politician practices than whether he or she practices any religion at all. A 2015 Gallup poll, for instance, found that 91 percent of Americans would support a Jew for president. Eighty-one percent would support a Mormon. Sixty percent would support a Muslim. But only 58 percent would back an atheist.

Sanders has not called himself an atheist. His secularism, however, may hurt him with voters who espouse a specific faith. According to a January 2016 Pew Research Center survey, Democrats who identified as Protestant or Catholic were roughly 20 points less likely than religious unaffiliated Democrats to say Sanders would make a good or great president. Among the religious unaffiliated within their party, Sanders led Clinton by eight points. But among Protestants and Catholics, she led him by 23 points.

During the presidential primaries, commentators dwelled on Sanders’ difficulty attracting African American voters. But the Pew survey shows that Sanders struggled among both black and white Democrats who identified with a religious tradition.

Should Sanders respond by going to synagogue and talking extensively about God? No. That wouldn’t be authentic, and authenticity is Sanders’ greatest political strength. But it’s one thing not to practice organized religion in one’s private life. It’s another to make a public show of it by scheduling major political speeches on your faith’s holiest days.

Sanders’ behavior typifies a secular tone-deafness that has long undermined both the American Jewish and Israeli left. It’s common knowledge that the further left an American Jewish organization is, the less likely it is to accommodate Jews who keep kosher or observe Shabbat. As a result, even the minority of Orthodox Jews who actually hold progressive political views sometimes find it hard to join progressive Jewish movements. Because of their focus on Israel, the Orthodox are more likely than other American Jews to vote on foreign policy, and thus, Sanders’ speech last Thursday might have been of particular interest to them. But Sanders was content for them not to hear it.

Unusually for people in his profession, Sanders is a man of unwavering principle. There is, however, a fine line between principle and rigidity. And while Sanders’ distaste for the superficial and symbolic elements of American politics is refreshing, especially in the age of Trump, the American presidency remains a highly symbolic job.

A president doesn’t only make public policy. He embodies national identity. That doesn’t mean Sanders must share the religious devotion that most Americans feel. But he’ll be more effective if he shows that he respects it.

Next year, perhaps, Sanders can spend Rosh Hashanah reading Isaac Deutscher or Berl Katznelson or even a book on Swedish dental policy, and leave the big speeches for another day. American Jews may give Sandy Koufax more credit than he deserves for not pitching on Yom Kippur. But it would be nice if the man who had received more votes for president than any Jew in American history weren’t determined to be Koufax in reverse.

Peter Beinart is a Forward senior columnist and contributing editor.