(NewsNation) — Americans are less religious than they used to be, but you wouldn’t know that by looking at the 118th Congress, which remains significantly more religious than the general public.

As part of an annual proclamation Thursday, President Joe Biden encouraged Americans of all faiths to recognize a “National Day of Prayer.”

In Congress, Christians still make up the large majority (88%) of the voting members, while only 63% of the general population consider themselves of the faith, according to Pew Research.

Today’s Congressional makeup is just slightly down from 1970 when 94% of lawmakers were Christian — a time when 90% of Americans identified as such.

Experts say the religious divergence between leadership and the public isn’t surprising, given the political considerations at play.

“Americans equate Christian with moral and that’s a nice bumper sticker for any politician,” said Phil Zuckerman, a professor of sociology and secular studies at Pitzer College.

For that reason, politicians have been reluctant to publicly identify as nonreligious and that difference explains most of today’s gap.

Only one member of Congress, Sen. Kyrsten Sinema, I-Ariz., openly identifies as religiously unaffiliated. U.S. Rep. Jared Huffman, D-Calif., describes himself as humanist and 20 other lawmakers are categorized as having unknown religious affiliations.

By comparison, nearly 30% of American adults today consider themselves “nonreligious.”

The religious composition of Congress over the decades

Protestants still make up the majority of lawmakers (57%) on Capitol Hill, though that proportion has fallen from 75% in the early 1960s.

Most of that change can be attributed to a rise in Catholics who now comprise 28% of Congress, up from 19% in 1961. That’s the same year John F. Kennedy became the first Catholic voted into the highest office. Biden is now the second.

The 118th Congress has 33 members who identify as Jewish, up from 19 in 1969, but comparable to the proportion throughout most of the 21st century.

Muslims, Hindus and Buddhists are represented in Congress in about equal proportion to their shares of the U.S. population, Pew found.

Both parties’ candidates more religious than their voters

Republicans in Congress are more likely than Democrats to identify as Christian but both delegations are more religious than members of their respective parties.

Almost 99% of GOP members of Congress are Christian, compared to 82% of Republicans in the general public. Congressional Democrats have more religious diversity but are significantly more likely to be Christian than their party’s voters — about 76% of Democratic lawmakers are Christian compared to 57% who identify with the party.

Much of that gap, Zuckerman thinks, can be explained by the polarization in today’s politics. As Christianity — particularly evangelical Protestantism — became more associated with former President Donald Trump and the political right, Democrats who may have previously identified with the faith were less eager to do so.

“If you were a middle-of-the-road, left-leaning or moderate American, suddenly you were like: ‘well, if that’s Christian my politics are trumping my religious identity right now,'” said Zuckerman.

That association could be particularly troubling for the GOP with young voters moving forward, Zuckerman said.

In the 2022 midterms, the religiously unaffiliated voted for Democratic House candidates over Republicans by more than a 2-1 margin (65% to 31%) nationwide, according to VoteCast. That’s in line with the 2020 presidential election, when Democrat Joe Biden took 72% of voters with no religious affiliation.

Age could also play a role

Older Americans are significantly more likely to identify with a religious group than younger generations and that could partially explain why members of Congress are more religious than the general public. The median age of voting House lawmakers is 57.9 years and 65.3 years in the Senate, whereas the average American is 39 years old.

“Most members of Congress skew old and they’ve been there as incumbents,” said Zuckerman. “The religious shifts we’re seeing of people becoming nonreligious… tend to skew younger.”

In other words, the age groups most likely to identify as nonreligious haven’t made it to Capitol Hill yet.

But it remains to be seen whether a generational turnover will lead to fewer religious lawmakers. This year’s Congressional newcomers, who were younger than incumbents on average, were just as likely to identify as Christian, Pew found.