Sept. 14, 2008— -- It's happened to John McCain and Barack Obama. Now it's Sarah Palin's turn to go through what one observer has called a "spiritual vetting."
For two decades, Palin was a member of an Assemblies of God church in her hometown of Wasilla, Alaska. In 2002, years before she was elected governor of Alaska, Palin and her family switched to a nondenominational church, but Palin still returns to her old church on special occasions.
There are an estimated 3 million worshippers in the Assemblies of God church in the Unites States, according to the Pew Forum on Religion and Public Life. Worldwide there are 500 million members, which is approximately 25 percent of all Christians. The Assemblies of God church is a form of Pentecostalism, which has become one of the fastest growing Christian movements in the world.
The most scrutinized and least understood aspect of the Assemblies of God Church and Pentecostalism in general is the ancient practice of "speaking in tongues."
"Speaking in tongues is a heavenly language," said Donna Morgan, a member of the Pennsylvania-based Freedom Valley Worship Center who embraces the experience. "That we're going to God and Jesus intercedes for us."
"It's almost as if I'm able to tap into God's heart and what he wants," said Amber Crone, who is also a member of the Freedom Valley Worship Center.
Pentecostalism has been described as evangelical experience on steroids. Like evangelicals, Pentecostals believe that the Bible is the literal word of God and that the end of time is near. However, Pentecostals also believe that the Holy Spirit can give you gifts such as speaking in tongues, prophesy, and divine healing.
"It's very common in Pentecostal churches to be emotionally involved, physically involved in our worship service," Palin's former pastor Tim McGraw said. "And the reason for that is that if you go to a football game and your team wins or kicks a field goal to win it's entirely consistent to be happy."
Other Christians have sometimes derided Pentecostals as "holy rollers," which may explain the defensiveness ABC News found when visiting an Assemblies of God Church in New Jersey this weekend.