Yesterday, a little less than a week before President’s Day, was Abraham Lincoln’s birthday. If he were alive today, he would be at the ripe age of 204. On the anniversary of the birth of one of the most respected presidents in American history, many would likely be surprised to learn this piece of Lincoln trivia: our 16^th President was one of only four religiously unaffiliated heads of state in American history.

As Americans have increasingly demanded greater insight into and knowledge of their presidents, religious beliefs have become an important part of a president’s public identity. Last May’s PRRI/RNS Religion News Survey found that more than 4-in-10 Americans (42%) believe it is somewhat important or very important for a presidential candidate to share their religious beliefs. Similarly, a 2011 Pew Survey found that 61% of Americans stated that they would be less likely to support a presidential candidate who does not believe in God. Lincoln was not an atheist, but these numbers indicate that his lack of religious affiliation would do more than raise a few eyebrows today.

Lincoln’s religion was also a point of debate and contention back in the mid-1800’s, before he was elected president.  During his run for a congressional seat in Illinois’ 7^th district, the Democratic contender, Peter Cartwright, publicly criticized Lincoln’s lack of faith. And the tactic worked, at least in part. Despite winning the congressional race in 1846, Lincoln lost in the two counties where Cartwright widely defamed Lincoln’s religious commitment.

The complexity of Lincoln’s religious beliefs and moral convictions continue to inspire debate among historians today. One incident that gives us a particularly revealing view of how Lincoln walked this fine line was his response to Cartwright’s criticism in a handbill accompanying a Letter to the Editor of the Lacon Illinois Gazette:

“That I am not a member of any Christian church is true; but I have never denied the truth of the Scriptures; and I have never spoken with intentional disrespect of religion in general, or of any denomination of Christians in particular…. I do not think I could myself be brought to support a man for office whom I knew to be an open enemy of, or scoffer at, religion.”

This letter echoes, without mirroring, many of the struggles faced by modern-day politicians. Religion was a notable issue in the early stages of the 2012 presidential race, when many white evangelical Protestants initially questioned whether the country should be governed by Mitt Romney, a Mormon. But it also raises questions about how Americans’ attitudes toward politics and religion have changed since Lincoln’s day. Would Lincoln’s views about religion and lack of formal affiliation be more controversial today – or in an increasingly religiously diverse society, would this matter less?