Bart Millard remembers the first time he realized I Can Only Imagine was a hit.
Nearly two years after his band, MercyMe, released the Christian song as a single in 2001, he got a call from a friend, saying he'd heard it on The Fitz Radio Program, a Dallas shock-jock show.
"Someone dared them to play Imagine," Millard says. "I turn on the station and all I hear is the DJ saying, 'Stop calling and we'll play it again.' For the next three or four hours, all they played was Imagine, and people were calling in, saying how much it meant to them. It was No. 1 on their station for, like, six months, up there with 50 Cent's In Da Club and some J.Lo song."
Since then, Imagine has become the best-selling Christian single of all time, selling 2.5 million copies, according to Nielsen Music (the only song in the genre to go double platinum). The emotional ballad — which considers what it would be like to go to heaven and meet God — is the rare Christian tune to cross over to country and pop radio, reaching No. 5 on Billboard's adult contemporary chart and No. 33 on the mainstream top 40.
It's now inspired a movie, I Can Only Imagine (in theaters nationwide Friday), which charts the difficult relationship between Millard (played by J. Michael Finley) and his abusive father (Dennis Quaid), who found God after his cancer diagnosis and became a better man. His death inspired Millard to write Imagine, which offered comfort after the Sept. 11 terror attacks.
"We heard a lot of people talking about losing loved ones and how 9/11 impacted them," he says. "I think the biggest thing is, there's no agenda: We're not trying to shove the Bible down anybody's throats. I'm asking the same question many people have wondered, whether you go to church or not, like, 'OK, God, if this turns out to be real, if we die and we get (to heaven), how am I going to respond?' There's no answers in that song, it's all questions."
Barry Alfonso, a music journalist and author of The Billboard Guide to Contemporary Christian Music, credits Imagine's breakout to timing, as fewer Christian artists were looking to pop as Jars of Clay and Amy Grant once had.
In the early 2000s, "the market was starting to get a little more segmented within itself, with different subgroups of Christian music and Christian bands," Alfonso says. "A song like I Can Only Imagine appealed to a very broad segment of Christian listeners and even beyond that. What it was saying and the way it was produced included the maximum amount of fans in that message," with a soulful, everyman quality to Millard's vocals that appealed to a mainstream audience.
Nearly two decades later, the faith-based film seems to be inspiring similar passion: Its trailer has notched 47 million views on Facebook, where the comments section is flooded with thousands of personal stories from those who have struggled with loss, depression and terminal illness.
"It's the best-selling Christian song ever, but when you talk to people about it, they go straight to talking about when they needed the song," says Andrew Erwin, who co-directed Imagine with his brother, Jon. "When we asked Bart, 'What does the song deliver?' He said, 'Unquestionably, a rush of hope.' "
Adds Jon: "It was one of those rare anomalies, and we need hope like we need oxygen. It's just one of those things that's necessary to have a fulfilling life. I believe we can give it to them in an even stronger way with the movie."