Conservatives went crazy yesterday when Barack Obama, who was participating in a project with documentary film maker Ken Burns to help Americans learn the Gettysburg Address, left out the phrase "under God" in his recitation of the speech. The video appeared on Burns’s “Learn the Address” website, which was created to commemorate the 150th anniversary of Lincoln’s famous speech at the dedication of the Gettysburg National Cemetery.

When I first heard this, I was very surprised. It just seemed so odd, especially after Obama took so much heat for inadvertently leaving out the word “Creator” in a 2010 speech referencing the Declaration of Independence. How could he make the same mistake twice?

But then I did some investigation. After spending less than a minute on the "Learn the Address" website, I found this statement: "Did you know there are five versions of the Gettysburg Address? We asked President Obama to read the first, the 'Nicolay Version'."

Indeed, there were multiple versions of the Gettysburg Address. The so-called Nicolay version, which was named after Lincoln’s personal secretary John Nicolay, was probably the first draft of the address. It is the earliest copy of the Gettysburg Address in existence. It does not contain the words “under God.”

There is no conspiracy here. Obama did not omit the words “under God” because he was trying to rewrite the Gettysburg Address as a secret ploy to promote a God-less society. Instead, he was participating in a history lesson. Perhaps this minor controversy will now alert many to the fact that there were different versions of the speech Lincoln gave on November 19, 1863.

I hope history teachers will recognize this and use the various versions of the Gettysburg Address to teach their students how to think deeply and critically about some of our nation’s most important historical documents.

In the age of the Common Core, where close reading of texts has taken on a new importance in schools, an exercise comparing and contrasting the various versions of the Gettysburg Address could produce a wonderful pedagogical moment.

But I do wonder why Obama's staff would have agreed to let him read the John Nicolay version? Surely they knew that it did not contain the "under God" reference. Surely they knew that his reading of this version might lead to a big political headache at a time when the president has enough problems to deal with concerning the Affordable Care Act? Surely someone did their homework and thought about the political implications of his reading of the Nicolay version?

But apparently Obama or his staff did not anticipate this problem. This is yet another case why we need more historians in Washington, D.C.