Michael Newdow sued her school and won, setting up the landmark appeal before a court that has repeatedly barred school-sponsored prayer from classrooms, playing fields and school ceremonies.
Americans overwhelmingly want the phrase "under God" preserved in the Pledge of Allegiance. Almost nine in 10 people said the reference to God belongs in the pledge, according to an Associated Press poll.
At Elk Grove Unified School District near Sacramento, where Newdow's daughter attends school, Superintendent Dave Gordon said popular opinion is on their side — but that's not all.
"The argument that 'under God' in the pledge is pushing religion on children is wrong on the law. It's also wrong from a commonsense perspective," Gordon said.
But Newdow compared the controversy to the issue of segregation in schools, which the Supreme Court took up 50 years ago in Brown v. Board of Education.
"Aren't we a better nation because we got rid of that stuff?" asked Newdow, a 50-year-old lawyer and doctor arguing his own case at the court.
The question put to the Supreme Court: Does the use of the pledge in public schools violate the Constitution's ban on government established religion?
The First Amendment guarantees that government will not "establish" religion, wording that has come to mean a general ban on overt government sponsorship of religion in public schools and elsewhere.
God was not part of the original pledge written in 1892. Congress inserted it in 1954, after lobbying by religious leaders during the Cold War. Since then, it has become a familiar part of life for a generation of students.
The Supreme Court has already said that schoolchildren cannot be required to recite the oath that begins, "I pledge allegiance to the flag of the United States of America."
Newdow sued the school, Congress, President Bush and others to eliminate the words. He asked for no damages.
A 9th U.S. Circuit Court of Appeals panel decided in June 2002 by a 2-1 margin that Newdow's daughter should not be subjected to the words "under God."
The court said the phrase was an endorsement of God, and the Constitution forbids public schools or other governmental entities from endorsing religion.
The 9th Circuit said the language of the First Amendment and the Supreme Court's precedents make clear that tax-supported schools cannot lend their imprimatur to a declaration of fealty to "one nation under God."
A national uproar followed the ruling. President Bush and Congress immediately condemned the decision. The full appeals court in February rejected the Bush administration's request to reconsider its decision. That set up the move to the Supreme Court.
"I don't believe there is a God. And why when I pledge allegiance to the flag or my child does in the school, why she should be forced to recite this account I don't agree with?" Newdow told the CBS News Early Show. "It was one nation indivisible. Then in 1954 the nation decided to divide our nation."
In its legal filings so far, the Bush administration has argued that the reference to God in the pledge is more about ceremony and history than about religion.
The reference is an "official acknowledgment of our nation's religious heritage," similar to the "In God We Trust" stamped on coins and bills, Solicitor general Theodore Olson told the court. It is far-fetched to say such references post a real danger of imposing state-sponsored religion, Olson wrote.
Moreover, being a parent of a child in public school does not give a parent the power to dictate what the child will be exposed to, Olson said.
"Public schools routinely instruct students about evolution, war and other matters with which some parent may disagree on religious, political or moral grounds," he said in his appeal.
If allowed to stand, the ruling would strip the reference from the version of the pledge recited by about 9.6 million schoolchildren in California and other western states.
Those states are Alaska, Arizona, California, Hawaii, Idaho, Montana, Nevada, Oregon and Washington. The effect of the ruling still is on hold.
Most legal experts think the high court will overturn the lower court ruling and uphold the pledge as is.
"I don't think the court would have taken the case merely to affirm what their colleagues in California had ruled," CBS News legal analyst Andrew Cohen said when the high court accepted the case.
The justices could eliminate the words by saying they were added for religious purposes, Cohen reports. Or justices could dodge the issue altogether. They have been urged to throw out the case, without a ruling on the constitutional issue, because of questions about whether Newdow had custody when he filed the suit and needed the mother's consent.
The girl's mother, Sandra Banning, is a born-again Christian and supporter of the pledge. She's has filed a brief opposing Newdow's action.
"I certainty don't want her to be remembered in American history as the child who was used as a means to change the pledge of allegiance," Banning told the Early Show.
Newdow says this battle has cost him over a million dollars, reports CBS News Correspondent Steve Futterman.
Absent from the case is one of the court's most conservative members, Justice Antonin Scalia, who bowed out after he criticized the ruling in Newdow's favor during a religious rally last year. Newdow had requested his recusal.