The self-described conservative Republican gained critical acclaim when his 2004 The Faith of George W Bush stayed for 15 weeks on the New York bestseller list. This year, he penned 'The Faith of Barack Obama' in which he dismissed question marks over Obama's commitment to Christianity.
"I believe that Barack Obama is a serious Christian, though of a theologically political liberal type," he said, according to a media release from his publishers, Thomas Nelson.
He acknowledged that many pro-lifers strongly disagree with Obama's support for abortion, but still urged people to be supportive towards America's 44th president.
"First and foremost, we should all pray for the new president," said Mansfield. "His challenges ahead are daunting and his vision must be clear."
In his book, 'The Faith of Barack Obama', Mansfield makes the case that at least part of Obama's vision for America is fuelled by his Christian faith.
"I believe that he will govern out of a religious base. He has already said that he'll continue many of President Bush's faith-based initiatives, and I wouldn't be surprised if he continued policies oriented towards prayer and bringing faith into the public square," he said.
Mansfield said it was important for people to know where the next president stands theologically.
"If he is serious about his religion, and I believe Barack Obama is, it is one of the most important things about him, it frames his world view, frames his sense of justice, frames his sense of right and wrong and therefore, frames his polices."
The Faith of Barack Obama has been endorsed by Archbishop Desmond Tutu, who said, "You must read this perceptive and well written book. Then you will know why Barack Obama has such a passion for justice and equity, such a gift for filling people of different generations with a newfound hope that things can and will change for the better.
"His inspiration comes from his faith; he is an ardent believer. Yes, he is a Christian and proud of it."
