As an undergraduate at Harvard, Richard Lyman Bushman was offered some friendly advice by a favorite professor: he was a fine student, but his Mormonism was seen by the Harvard establishment as a "bunch of garbage."

Bushman would do himself a favor, the professor told him, to leave the Church of Jesus Christ of Latter-day Saints behind as a relic of his upbringing.

"I reacted just the opposite," Bushman said in a phone interview. "I said, 'You're not going to bully me, you big representative of Harvard culture."'

That was 57 years ago. Since then, Bushman has retained his Mormon faith even while forging an Ivy League academic career, earning posts at Columbia and Harvard.

In fact, as his teaching and research focused on colonial American history, Bushman also managed to become something of an ambassador for Mormonism to the outside world.

Now, with the presidential candidacy of Mitt Romney (whom Bushman knew when both were at Harvard in the '70s and whose son is a member of Bushman's New York congregation), Bushman is being thrust further into the public spotlight, becoming the nation's chief defender and explainer of Mormonism.

When The New Republic published a cover article in January questioning whether a Mormon was fit to be president, the magazine asked Bushman to write a "Mormon" response. At the Pew Forum on Religion & Public Life's journalism conference in May, Bushman was asked to lead a session titled "Mormonism and Democratic Politics: Are They Compatible?"

And as news media outlets run stories about the current "Mormon moment," his phone keeps ringing. He considered it a blessing that he was already on his way out of New York for his annual summerlong sojourn in Provo, Utah, when "Good Morning America" and "The Daily Show" started calling.

"I'm still kind of a babe in the woods when it comes to TV," Bushman, 76, said from Provo, where he is joined by his wife, Claudia, who has also taught at Columbia and has written books on Mormonism with him.

And yet he says his stomach for so many media appearances, answering the same questions over and over, is born of duty to his faith. He believes Mormons can overcome prejudice only through vigorous dialogue with outsiders. For the nation's nearly six million Mormons, a largely insulated community that is barred from discussing rituals outside of temple, it is not a natural posture.