House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell and Senate Minority Leader Harry Reid bow their heads in prayer in this 2015 photo. All three are Christians, as are more than 90 percent of congressional members.
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Republican presidential candidate Donald Trump holds up a Bible that was given to him by his mother as he speaks during the Values Voter Summit in Washington, D.C., on Sept. 25, 2015.
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Hillary Clinton attends church with daughter Chelsea Clinton at the Greater Mount Carmel Missionary Baptist Church in St. Louis, Missouri while on the campaign trail in 2008.
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State Sen. Ferrell Haile, R-Gallatin (left), speaks during debate on a bill that would make the Bible the state book of Tennessee. At front right is Sen. Steve Southerland, R-Morristown, who sponsored the bill.
For the first time since their churches split in the 11th century, Pope Francis and Russian Orthodox Patriarch Kirill will meet in person. They're seen here in photos from earlier this year.
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Texas Sen. Ted Cruz speaks during the 2015 Iowa Faith & Freedom Coalition presidential forum. He's made religion a central tenet of his campaign for the Republican presidential nomination.
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