What happens when the tail is low is that as the plane gains speed the wing (and tail) forces the nose into the ground and won't allow the airplane to take off unless you have alot of power. If you have enough power it will lift straight up. The wing wants to fly level and the tail does also so they are lifting the main gear and plowing the nose. This creates the situation you described. With the tail level or slightly (or even greatly) above level as the plane gains speed the wing and tail want to rotate the nosewheel off the ground and past allowing the plane to take off with alot less power. Lifting the nosewheel off the ground eliminates the drag of the nosewheel.
I have seen this situation alot on trainers in particular where people have great difficulty getting off the runway.