This has been a topic of intense debate for decades now. And though the evidence available is circumstantial at best, I think it's still an interesting question.
Contrary to popular belief, Abraham Lincoln's personal religious beliefs were anything but orthodox. The man never officially joined a church during his life and rarely if ever openly supported any major religion. With that said, this should not automatically insinuate that Lincoln was a man without faith.
In a recent email from a friend of mine was a link to an interesting piece regarding Joseph Smith and Abraham Lincoln. And while these two men share very little in common, I was struck by some of their similarities. As most of you know, Smith was himself a bit of a religious rogue, who never joined any one church. Instead, Smith founded his own religion, which as my fellow American Creation co-blogger, Jon Rowe has pointed out on numerous occasions, can be compared to the religion of many of the key Founding Fathers. This comparison is not made in the sense that the founders shared the same beliefs as Mormons (though there are a few similarities with a select few founders) but from the fact that both Mormons and many founders are/were seen as "heretics," due to the fact that they are not followers of traditional orthodox Christianity. In this respect, the same can be said of Lincoln, who in the following article (you an access it by clicking here) may have met the Mormon prophet on more than one occasion. If so, did Lincoln develop an interest (albeit a very loose one) in Mormonism? From his writings, Lincoln was quite kind to the "Mormon plight." In fact, one of the last books he read before being killed was The Book of Mormon. Could Lincoln have developed a sympathy for a religion that was as unorthodox as the 16th President himself?
In any case, I hope you will enjoy the article!