Young Americans are drifting away from God, according to a new Pew Research Center poll. Only 67 percent of Americans under 30 say they "never doubt the existence of God." That's down from 76 percent in 2009 and 83 percent in 2007 — a 15 percentage point drop in just five years. Why the big change? Here, three theories:

1. Fundamentalists are turning off some young people

Blame it on the Religious Right, says Stephanie Mencimer at Mother Jones. "Younger Christians are turned off by attacks on gays and lesbians." Baby boomers and older Americans have believed in God for so long, says James Joyner at Outside the Beltway, that their religious beliefs don't falter as our society rapidly evolves toward greater acceptance of divorce, premarital sex, women's equality, and gay rights. "Younger folks are simply more likely to figure that, if their religion is teaching them things that they believe to be silly — such as that homosexuality is wrong — then their religion must be silly, too."

2. Atheists and agnostic role models are getting more vocal

Older Americans are holding fast to their beliefs, says Sahil Kapur at Talking Points Memo, with 80 percent to 90 percent saying that they never doubt God's existence. But younger Americans have been exposed to "a new movement of atheist or agnostic thinking during the last decade — spearheaded by high-profile authors like Richard Dawkins, Christopher Hitchens, and Sam Harris." This poll appears to confirm that these influential intellectuals are "steering younger people away from traditional beliefs long held by their parents." With greater acceptance, says Ronald A. Lindsay at The Huffington Post, young atheists are finding it safe to "come out."

3. Liberal attacks on religion are to blame

Christianity is "the one religion left that can be hated without running afoul of political correctness," says Drew Belsky at The American Thinker. In an era when the federal government is forcing religious institutions, contrary to their religious beliefs, to give people insurance coverage for contraception, says Bishop Edward Burns at The Southeast Alaska Catholic Online, it's pretty undeniable that religion, and religious freedom, are under siege. Most Americans still believe in God, but they have to defend their faith or the attacks will take a toll.