NEW YORK -- No one except a few insiders has seen it. Yet a "Celebrate Family, Celebrate Life" ad featuring football star Tim Tebow and paid for by a conservative Christian group is already perhaps the most hotly debated Super Bowl commercial ever.
When the 30-second ad finally airs in the first quarter of Sunday's CBS telecast -- at a cost estimated at $2.5 million -- it's expected to show the devout quarterback and his mother, Pam, sharing the story of how she gave birth to him in the Philippines in 1987 after spurning a doctor's advice to have an abortion for medical reasons.
In the past two weeks, as news of the ad spread, it has generated a vast, often passionate national discussion -- the subject of countless newspaper columns, blogs and tweets and fodder for dozens of advocacy groups to spar over abortion, women's rights and free speech.
Broadcasting and marketing experts say it's the first politically tinged advocacy ad ever with a national buy on a Super Bowl. The audience is projected at 100 million viewers.
The idea for ad originated last year with a staff member at Focus on the Family, an evangelical Christian organization based in Colorado Springs, Colo., that provides advice on marriage and parenting and has also campaigned vigorously against abortion, same-sex marriage and comprehensive sex education.
Focus found willing partners in Pam Tebow, a missionary and evangelist, and her youngest son, whose Heisman Trophy-winning career at Florida was interspersed with missionary outreach of his own.
Only on Jan. 15 did plans for the ad become public, when Focus issued a press release about it. Initially, Focus was coy about the ad's precise message, but president and CEO Jim Daly was more explicit in a video posted online Thursday.
"Over 50 million children have lost their lives due to abortion," Daly said. "We simply want to ask people the question: Can we do better? I think we can."
The controversy over the ad was slow to build but ignited on Jan. 25 when the National Organization for Women, the Feminist Majority and other liberal women's groups launched a protest campaign aimed at pressuring CBS to scrap the ad. Abortion-rights advocates joined in.
"We support every woman's ability to make the decisions that are best for her and her family," said Nancy Keenan, president of NARAL Pro-Choice America. "But Focus on the Family wants to take options away from women."
Anti-abortion groups and other conservative activists swiftly mounted a counterattack, denouncing the campaign against the ad as a clumsy attempt to squelch free speech. But the ensuing back-and-forth did not break down neatly along ideological lines.
The New York Times, for example, supports abortion rights in its editorials but disagreed with those calling for the ad to be withdrawn.
"Viewers can watch and judge for themselves," the Times said. "Or they can get up from the couch and get a sandwich."
Other examples of how the controversy has played out:
Plans for a media availability with Tebow inside the Super Bowl media center were abruptly canceled Friday, shortly after reporters were told no questions would be answered about the ad. Tebow walked out of the area flanked by about a dozen people including security, only saying "Sorry" when asked if he would stop to take questions.
Focus on the Family confirmed it has purchased air time on a CBS pregame show for a different version of the Tebow ad that will air during the game.
In Michigan, a Republican congressional candidate, former NFL player Jay Riemersma, plans to host a pre-Super Bowl rally Sunday in support of the ad.
Planned Parenthood, which supports abortion rights and often spars with Focus on the Family, produced an online video response to the Tebow ad. It features former NFL player Sean James and Olympic gold medal winner Al Joyner talking about the importance of women being able to make their own health decisions without government interference.
The Susan B. Anthony List, an anti-abortion group, launched a Web site called blockhardfortebow.com and said more than 50,000 people submitted comments in support of Tebow and the TV ad.
All along, CBS stuck by its decision to air the ad while announcing that it would be receptive to other "responsibly produced" advocacy ads -- a shift from a past policy that kept Super Bowl commercial time free from political and ideological messages.
"CBS is potentially going to revolutionize network advertising for big events with this," said Charles Taylor, professor of marketing at Villanova School of Business. "I'd hate to see an event like the Super Bowl become partly an advocacy contest."
In the future, Taylor said, Super Bowl broadcasters might face demands for air time from opposing sides on divisive issues.
There have been plenty of past controversies over Super Bowl ads, but generally it's been a question of taste, or lack of it.
The Go Daddy Group Inc., for example, welcomes debate over its risque ads. This year, it has made available online a provocative spot that was rejected by CBS -- featuring a fictional ex-NFL player savoring his new career as an effeminate lingerie designer.
After the 2007 Super Bowl, the General Motors Corp. drew criticism from a suicide prevention group for showing a robot jumping off a bridge in a dream sequence after messing up on the job.
According to a Marist poll released Friday, Americans are conflicted about some of the issues raised by the ad brouhaha.
Asked about advocacy ads during the Super Bowl, 49 percent of the poll respondents said they were inappropriate and 44 percent said they were acceptable. But 60 percent supported the decision by CBS to air the Tebow ad.
Like the ad or not, it will appear Sunday evening, along with pitches for beer and soft drinks, cars and candy bars, Denny's restaurants and the new "Dante's Inferno" video game. Among the many Americans who annually watch partly because of the ads, there's been some notes of regret.
"The Super Bowl is a time for football and idiotic, lighthearted commercials," wrote freshman Lauren Hadley in the University of South Carolina's student paper. "It's not the appropriate time to preach ethics and morals to America."