Reuters A women and her son buy Christmas decorations at a shop in Colombo December 14, 2009.

By AMY SULLIVAN /For Time / Washington Tue Dec 15, 3:10 am ET: If it’s December, then there must be frost in the air, gingerbread in the oven, and … right on time, Bill O’Reilly and the other defenders of Christmas bemoaning the prevalence of “Happy Holidays” – rather than “Merry Christmas” – greetings.

There’s a war on Christmas, O’Reilly recently reminded viewers, driven by those who “loathe the baby Jesus.” This season, a holiday-dȣor company is marketing the CHRIST-mas Tree, a bushy artificial tree with a giant cross where the trunk should be. And the Colorado-based Focus on the Family is continuing its Stand for Christmas campaign to highlight the offenses of Christmas-denying retailers. The campaign was launched, according to its website, because “citizens across the nation were growing dissatisfied with the tendency of corporations to omit references to Christmas from holiday promotions.” (See TIME’s photoessay “Have a Very Ridiculous Christmas.”)

But to a growing group of Christians, this focus on the commercial aspect of Christmas is itself the greatest threat to one of Christianity’s holiest days. “It’s the shopping, the going into debt, the worrying that if I don’t spend enough money, someone will think I don’t love them,” says Portland pastor Rick McKinley. “Christians get all bent out of shape over the fact that someone didn’t say ‘Merry Christmas’ when I walked into the store. But why are we expecting the store to tell our story? That’s just ridiculous.”

McKinley is one of the leaders of an effort to do away with the frenzied activity and extravagant gift-giving of a commercial Christmas. Through a savvy viral video and marketing effort, the so-called Advent Conspiracy movement has exploded. Hundreds of churches on four continents and in at least 17 countries have signed up to participate. The Advent Conspiracy video has been viewed more than a million times on YouTube and the movement boasts nearly 45,000 fans on Facebook. Baseball superstar Albert Pujols is a supporter – he spoke at a church event in St. Louis to endorse the effort. (See TIME’s video “Bethlehem’s Complicated Christmas.”)

In the past four years, Advent Conspiracy churches have donated millions of dollars to dig wells in developing countries through Living Water International and other organizations. McKinley likes to point out that a fraction of the money Americans spend at retailers in the month of December could supply the entire world with clean water. If more Christians changed how they thought about giving at Christmas, he argues, the holiday could be transformative in a religious and practical sense.

The idea for their own war on Christmas came to McKinley four years ago, when he was sitting around with some of his pastor friends and they realized they were all dreading Christmas. “None of us like Christmas,” he says, adding, “That’s sort of bad if you’re a pastor.” Instead of helping their congregations focus on the season of Advent and prepare to celebrate the birth of Christ, the pastors found themselves competing with a secular consumerism that made December the hardest time to make their message heard.

So McKinley and his friends decided to try a radical experiment. They urged congregants to spend less on presents for friends and family, and to consider donating some of the money they saved as a result. At first, church members weren’t quite sure how to react. “Some people were terrified,” remembers McKinley. “They said, ‘My gosh, you’re ruining Christmas. What do we tell our kids?'” The pastors had to reassure people that they weren’t advocating a Grinchy no-gifts kind of Christmas, but rather one in which people spent a little less and thought a little more, expressing their love through something more meaningful than a gift card. Once church members adjusted to this new conception of Christmas, they found that they loved it. Many, in fact, seemed relieved to be given permission to slow down and buy less. (Read “A Brief History of ‘The War on Christmas'”)

In many ways, the Advent Conspiracy movement has appropriated some of the traditional arguments of the conservative Christians who see themselves as defenders of Christmas. A popular rallying cry of the foot soldiers in the war on Christmas is, “Jesus is the reason for the season.” Often, however, it seems that being able to score a half-price Nintendo DSi and a “Merry Christmas” from the checkout clerk is the real prize. The Religious Right has spent decades casting secular culture as the enemy. And yet instead of critiquing the values of the consumer marketplace, many conservative Christians have embraced it as the battleground they seek to reclaim.

A movement like the Advent Conspiracy is countercultural on two fronts – not just fighting the secular idea that Christmas is a month-long shopping and decorating ritual, but the powerful conservative notion that the holiday requires acknowledgement from the nation’s retailers to be truly meaningful. It’s not easy, says one youth pastor whose church is part of the Advent Conspiracy. “When you start jacking with people’s idea of what Christmas is and you start to go against this $450 billion machine of materialism and consumerism, it really messes with people,” he explains. “It takes a lot of patience to say there’s a different way – Christmas doesn’t have to be like this.”