However, I am inclined to believe they wanted him to fall. If they had been serious about keeping it upright, they likely would have tasked the same aides discussed in this story to stay close to him:
Biden Aides Forced To Use The Spray Bottle Again
After all, one of them has to stay close anyway, just giving him or her a task when there are no little girls or women with long hair nearby would simply be an efficient use of campaign money.