Each morning for the past five years, before most of his aides even arrive at the White House, Obama has read a devotional written for him and sent to his BlackBerry, weaving together Scripture with reflections from literary figures such as Maya Angelou and C.S. Lewis.
"I've certainly seen the president's faith grow in his time in office," said Joshua DuBois, an informal spiritual adviser to Obama who writes the devotionals and ran Obama's faith-based office until earlier this year. "When you cultivate your faith, it grows."
Obama is particularly moved by theories that draw connections between biblical themes and the personal journeys of historical figures such as Abraham Lincoln and Martin Luther King Jr., DuBois said.
He added that the president's spiritual strength is his belief that God will carry him through to see another day even in times of crisis.
"Because of these grounding aspects of his life, he doesn't let the day-to-day challenges really shake him," said DuBois, a former associate pastor at a Pentecostal church.
The image of Obama as someone who draws heavily on faith to guide his daily life contrasts with his public persona.
An intensely private person, Obama has shied away from all but the most general descriptions of his spiritual life.
Obama had to distance himself from his longtime pastor, the Rev. Jeremiah Wright, when his anti-American rantings threatened Obama's 2008 presidential campaign.
Persistent and false claims that Obama is secretly a Muslim have followed him even into his second term.
"Sometimes I search Scripture to determine how best to balance life as a president and as a husband and as a father," Obama said in February at the National Prayer Breakfast. "I often search for Scripture to figure out how I can be a better man as well as a better president."
The best clues to which texts fortify Obama's spiritual consumption may come from the daily devotionals that DuBois started sending Obama, then a U.S. senator from Illinois, in 2008.
DuBois ran religious outreach for Obama's presidential campaign that year, and his digital benedictions for Obama have been compiled in a forthcoming book, "The President's Devotional."
"A snippet of Scripture for me to reflect on," Obama has said. "And it has meant the world to me."
At pivotal moments in Obama's presidency, DuBois sometimes selects texts that offer lessons appropriate to the challenges at hand.
Before one State of the Union address, it was the words of Isaiah, in an appeal for clarity of speech: "So shall my word be that goes out from my mouth, it shall not return to me empty, but it shall accomplish that which I purpose."