It's interesting you mention Ayn Rand. She - and modern libertarianism in general - are not classical liberalism. They are a Romantic (mis)interpretation of classical liberalism.
“Cabalistic Christianity, which is Catholic Christianity, and which has prevailed for 1,500 years, has received a mortal wound, of which the monster must finally die. Yet so strong is his constitution, that he may endure for centuries before he expires.”
— John Adams, letter to Thomas Jefferson, July 16, 1814
“What havoc has been made of books through every century of the Christian era? Where are fifty gospels condemned as spurious by the bull of Pope Gelasius? Where are forty wagon-loads of Hebrew manuscripts burned in France, by order of another pope, because of suspected heresy? Remember the Index Expurgato-rius, the Inquisition, the stake, the axe, the halter, and the guillotine; and, oh! horrible, the rack! This is as bad, if not worse, than a slow fire. Nor should the Lion’s Mouth be forgotten. Have you considered that system of holy lies and pious frauds that has raged and triumphed for 1,500 years.”
— John Adams, letter to John Taylor, 1814, quoted by Norman Cousins in In God We Trust: The Religious Beliefs and Ideas of the American Founding Fathers (New York: Harper & Brothers, 1958), p. 106-7, from James A Haught, ed, 2000 Years of Disbelief
“God is an essence that we know nothing of. Until this awful blasphemy is got rid of, there never will be any liberal science in the world.”
— John Adams, “this awful blashpemy” that he refers to is the myth of the Incarnation of Christ, from Ira D Cardiff, What Great Men Think of Religion
“... the Common Law existed while the Anglo-Saxons were yet pagans, at a time when they had never yet heard the name of Christ pronounced or knew that such a character existed.”
— Thomas Jefferson, letter to Major John Cartwright, June 5, 1824.
“In the affairs of the world, men are saved, not by faith, but by the want of it.”
“I have found Christian dogma unintelligible. Early in life, I absenteed myself from Christian assemblies.”
— Benjamin Franklin
“The founders of our nation were nearly all Infidels, and that of the presidents who had thus far been elected [Washington; Adams; Jefferson; Madison; Monroe; Adams; Jackson] not a one had professed a belief in Christianity.”
“Among all our presidents from Washington downward, not one was a professor of religion, at least not of more than Unitarianism.”
— The Reverend Doctor Bird Wilson, an Episcopal minister in Albany, New York, in a sermon preached in October, 1831. One might expect a modern defender of the Evangelical to play with the meaning of “Christianity,” making it refer only to a specific brand of orthodoxy, first sentence quoted in John E Remsberg, Six Historic Americans, second sentence quoted in Paul F Boller, George Washington & Religion, pp. 14-15
Imagine current presidential candidates making such opinions heard out loud. They need to feign belief, like Obama.