When Pope Francis addresses Congress on Thursday, he will face a body that is more Christian than the U.S. public as a whole — and also more Catholic.
First the numbers: Whereas nearly a quarter of the U.S. population says they have no religious affiliation, it's less than 1 percent in Congress.
Congress is "disproportionately religiously affiliated," said Alan Cooperman, director of religion research at the Pew Research Center. "That is, the share of members of Congress who say they have a religion is considerably higher than the share of all American adults."
In the halls of Congress, the question of why this might be was greeted with puzzlement and some theories:
"Maybe it's because we need the solid grounding and good guidance that we get from above," said Shelley Moore Capito, a senator from West Virginia.
"Maybe it has something to do with the magnitude of issues we deal with up here and people realize that you can't do that without a degree of reliance on spiritual need," said Sen. Richard Burr of North Carolina.
Surveys show that the public overwhelmingly wants their presidents to have religion in their lives. So it makes sense that it would carry over to congressional elections, too. Sen. Gary Peters from Michigan is Episcopalian, and he said his spirituality is important to him and "gives me comfort in rough times."
He figures, at least for some voters, knowing that he has a religious grounding helps them trust him.
"They want to look you in the eye," he said. "They want to get a sense of what sort of man or woman that you are. ... I think it's that intangible quality ... you have to just be who you are and if your spiritual soul is part of that, then that's ultimately how they're going to make decisions as to who they support."
Another possible reason — members of Congress are often asked to state their religion. Chris Murphy, a senator from Connecticut, checks the box "unspecified/other Protestant."
"I grew up in a congregational church," he said. "I'm not a regular churchgoer these days, in part, because of kids. In part because of a busy schedule."
Pew found members of Congress are more religiously affiliated, but it doesn't say anything about whether they are actually more religious than the rest of America. The Senate's longtime chaplain, Barry Black, thinks they are, based at least on the popularity of his weekly interfaith prayer breakfasts.
"Now I don't think you'd get a similar percentage from normal churchgoers if you were having an hour prayer breakfast each week during the workweek," he said.
Black cites the Psalm 119: Before I was afflicted, I went astray but now I obey your word.
"So I think there is something about affliction — and, trust me, going through the legislative process can be an experience of affliction — that helps people to probably be more spiritual," he said.
What he seems to be saying is you'd be more religious, too, if you had to serve in Congress.