President Obama has come out swinging against his Republican rival, sponsoring television advertisements that ask, "What is Mitt Romney hiding?" The allusion is to such relatively minor matters as Mr. Romney's prior tax returns, the date he stopped working for Bain Capital and the nonpublic records from his service heading the Salt Lake City Olympics and as governor of Massachusetts. Mr. Obama has defended his demands that Mr. Romney release more information about himself, declaring in August that "the American people have assumed that if you want to be president of the United States that your life's an open book when it comes to things like your finances." Liberals such as Paul Krugman of the New York Times enthusiastically endorse this focus on Mr. Romney's personal history.

If President Obama and his supporters wish to focus on biography, of course, that is a game two can play. Already, the temperate, mild-mannered Mr. Romney has criticized Mr. Obama's re-election campaign as "based on falsehood and dishonesty," and a television ad went further, asserting that Mr. Obama "doesn't tell the truth."

A focus on openness and honesty is likely to hurt Mr. Obama far more than Mr. Romney. Mr. Obama remains the mystery candidate with an autobiography full of gaps and even fabrications. For example, to sell his autobiography in 1991, Mr. Obama claimed that he "was born in Kenya." He lied about never having been a member and candidate of the 1990s Chicago socialist New Party. When Stanley Kurtz produced evidence to establish that he was a member, Mr. Obama's flacks smeared and dismissed Mr. Kurtz. Mr. Obama's 1995 autobiography, Dreams from My Father, contains a torrent of inaccuracies and falsehoods about his maternal grandfather, his father, his mother, his parents' wedding, his stepfather's father, his high school friend, his girlfriend, Bill Ayers and Bernardine Dohrn, and the Rev. Jeremiah Wright. As Victor Davis Hanson put it, "If a writer will fabricate the details about his own mother's terminal illness and quest for insurance, then he will probably fudge on anything."

Into this larger pattern of mendacity about his past life arises the question of Mr. Obama's discussion of his faith, perhaps the most singular and outrageous of his lies.

Asked about the religion of his childhood and youth, Mr. Obama offers contradictory answers. He finessed a March 2004 question, "Have you always been a Christian?" by replying: "I was raised more by my mother and my mother was Christian." But in December 2007, he belatedly decided to give a straight answer: "My mother was a Christian from Kansas. I was raised by my mother. So, I've always been a Christian." In February 2009, however, he offered a completely different account:

"I was not raised in a particularly religious household. I had a father who was born a Muslim but became an atheist, grandparents who were non-practicing Methodists and Baptists, and a mother who was skeptical of organized religion. I didn't become a Christian until I moved to the South Side of Chicago after college."

He further elaborated on this answer in September 2010, saying, "I came to my Christian faith later in life."

Which is it? Has Mr. Obama "always been a Christian" or did he "become a Christian" after college? Self-contradiction on so fundamental a matter of identity, when added to the general questioning about the accuracy of his autobiography, raises questions about veracity. Would someone telling the truth say such varied and opposite things about himself? Inconsistency is typical of fabrication: When making things up, it's hard to stick with the same story. Mr. Obama appears to be hiding something. Was he the areligious child of irreligious parents? Or was he always a Christian? A Muslim? Or was he, in fact, something of his own creation -- a Christian Muslim?

Mr. Obama provides some information on his Islamic background in his two books, Dreams from My Father and The Audacity of Hope (2006). In 2007, when Hillary Rodham Clinton was still the favored Democratic candidate for president, a number of reporters dug up information about Mr. Obama's time in Indonesia. His statements as president have provided important insights into his mentality. The major biographies of Mr. Obama, however, whether friendly (such as those by David Maraniss, David Mendell and David Remnick) or hostile (such as those by Jack Cashill, Jerome R. Corsi, Dinesh D'Souza, Aaron Klein, Edward Klein and Stanley Kurtz), devote little attention to this topic.

I shall establish his having been born and raised a Muslim, provide confirming evidence from recent years, survey the perceptions of him as a Muslim, and place this deception in the larger context of Mr. Obama's autobiographical fictions.

To begin with, Barack Obama readily acknowledges that his paternal grandfather, Hussein Onyango Obama, converted to Islam. Indeed, Dreams (Page 407) contains a long quote from his paternal grandmother explaining the grandfather's reasons for doing so: Christianity's ways appeared to be "foolish sentiment" to him, "something to comfort women," and so he converted to Islam, thinking "its practices conformed more closely to his beliefs" (Page 104). Barack Obama readily told this to all comers: When asked by a barber (Page 149), "You a Muslim?" for example, he replied, "Grandfather was."

Many pieces of evidence argue for Barack Obama having been born and raised a Muslim:

(1) Islam is a patrilineal religion: In Islam, the father passes his faith to the children, and when a Muslim man has children with a non-Muslim woman, Islam considers those children Muslim. Mr. Obama's grandfather and father having been Muslims -- the extent of their piety matters not at all -- means that in Muslim eyes, Mr. Obama was born a Muslim.

(2) Arabic forenames based on the H-S-N trilateral root: All such names (Husayn or Hussein, Hasan, Hassan, Hassanein, Ahsan and others) are exclusively bestowed on Muslim babies. (The same goes for names based on the H-M-D root.) Mr. Obama's middle name, Hussein, explicitly proclaims him born a Muslim.

(3) Registered as Muslim at SD Katolik Santo Fransiskus Asisi: Mr. Obama was registered at a Catholic school in Jakarta as "Barry Soetoro." A surviving document correctly lists him as born in Honolulu on Aug. 4, 1961. In addition, it lists him as having Indonesian nationality and Muslim religion.

(4) Registered as Muslim at SD Besuki: Although Besuki (also known as SDN 1 Menteng) is a public school, Mr. Obama curiously refers to it in The Audacity of Hope (Page 154) as "the Muslim school" he attended in Jakarta. Its records have not survived, but several journalists (Haroon Siddiqui of the Toronto Star, Paul Watson of the Los Angeles Times and David Maraniss of The Washington Post) all have confirmed that there, too, he was registered as a Muslim.

(5) Islamic class at Besuki: Mr. Obama mentions (Audacity, Page 154) that at Besuki, "the teacher wrote to tell my mother that I made faces during Koranic studies." Only Muslim students attended the weekly two-hour Koran class, Mr. Watson reports:

"Two of his teachers, former Vice Principal Tine Hahiyari and third-grade teacher Pak Effendi, said they remember clearly that at this school, too, he was registered as a Muslim, which determined what class he attended during weekly religion lessons. 'Muslim students were taught by a Muslim teacher, and Christian students were taught by a Christian teacher,' Mr. Effendi said."

Andrew Higgins of The Washington Post quotes Rully Dasaad, a former classmate, saying that Barack Obama horsed around in class and, during readings of the Koran, got "laughed at because of his funny pronunciation." Mr. Maraniss learned that the class included not only studying "how to pray and how to read the Koran" but also actually praying in the Friday communal service on the school grounds.

(6) Mosque attendance: Maya Soetoro-Ng, Mr. Obama's younger half-sister, said her father (Mr. Obama's stepfather) attended the mosque "for big communal events." Kim Barker of the Chicago Tribune found that "Obama occasionally followed his stepfather to the mosque for Friday prayers."

The childhood friends say Mr. Obama sometimes went to Friday prayers at the local mosque. "We prayed but not really seriously, just following actions done by older people in the mosque. But as kids, we loved to meet our friends and went to the mosque together and played," said Zulfin Adi, who described himself as among Mr. Obama's closest childhood friends. Sometimes, when the muezzin sounded the call to prayer, Lolo and Barry would walk to the makeshift mosque together, Mr. Adi said. "His mother often went to the church, but Barry was Muslim. He went to the mosque," Mr. Adi said.

(7) Muslim clothing: Mr. Adi recalls about Mr. Obama, "I remember him wearing a sarong." Likewise, Mr. Maraniss found not only that "his classmates recalled that Barry wore a sarong," but written exchanges indicating that he continued to wear this garment in the United States. This fact has religious implications because in Indonesian culture, only Muslims wear sarongs.

(8) Piety: Mr. Obama said that in Indonesia, he "didn't practice" Islam, an assertion that inadvertently acknowledges his Muslim identity by implying he was a nonobservant Muslim. But several of those who knew him contradict this recollection. Rony Amir described Mr. Obama as "previously quite religious in Islam." A former teacher, Tine Hahiyary, quoted in the Kaltim Post, said the future president took part in advanced Islamic religious lessons: "I remember that he had studied mengaji." In the context of Southeast Asian Islam, mengaji Koran means to recite the Koran in Arabic, a difficult task denoting advanced study.

In summary, the record points to Barack Obama having been born a Muslim to a non-practicing Muslim father and having lived for four years in a fully Muslim milieu under the auspices of his Muslim Indonesian stepfather. For these reasons, those who knew Mr. Obama in Indonesia considered him a Muslim.

Several statements by Barack Obama in recent years point to his Muslim childhood.

(1) Robert Gibbs, campaign communications director for President Obama's first presidential race, asserted in January 2007: "Sen. Obama has never been a Muslim, was not raised a Muslim, and is a committed Christian who attends the United Church of Christ in Chicago." But he backtracked in March 2007, asserting that Mr. Obama "has never been a practicing Muslim." By focusing on the practice as a child, the campaign is raising a nonissue, for Muslims (like Jews) do not consider practice central to religious identity. Mr. Gibbs added, according to a paraphrase by Paul Watson of the Los Angeles Times, that "as a child, Obama had spent time in the neighborhood's Islamic center." Clearly, "the neighborhood's Islamic center" is a euphemism for a mosque. Spending time there again points to Mr. Obama's being a Muslim.

(2) He may have made faces and horsed around in Koran class, but Mr. Obama learned how to pray the salat, a form of ritual worship, in religion class. Pak Effendi, his former teacher at Besuki, his school in Jakarta, Indonesia, recalls that he would "join the other pupils for Muslim prayers." Praying the salat in and of itself made Mr. Obama a Muslim. Furthermore, he still proudly retains knowledge from that long-ago class. In March 2007, Nicholas D. Kristof of the New York Times witnessed as Mr. Obama "recalled the opening lines of the Arabic call to prayer, reciting them [to Mr. Kristof] with a first-rate accent." Mr. Obama recited not the salat itself but the adhan, the call to prayer (typically chanted from minarets). The second and third lines of the adhan constitute the Islamic declaration of faith, the shahada, the very utterance of which makes one a Muslim. The full adhan in its Sunni iteration (skipping the repetitions) goes as follows: