Tennessee was not the only state that almost sided with the Union in the Civil War. Other states considered siding with the Union as well. Unfortunately, "almost" is irrelevant in history. What remains important is what did happen, and that is that Tennessee was a confederate state. "What if?" generally does not hold a lot of weight in the study of history.
Yes, I am aware of Tennessee's involvement in the Civil War as I was raised in Tennessee. However, the notion that Tennessee almost "went Union" is a bit misguided. Tennessee was the last State to leave the Union and only did so among mounting pressure. When the time came to rejoin the Union, Tennessee was also the first to do so.
This is a basic historical fact and I have no idea why it's being treated as a debate question. Yes I was aware of this, how much further can we go with this? I do not understand the purpose of this question, as it really makes no sense in the context of a debate.