hang in the balance

To be perilously close to failing, depending on the outcome of something. The court is just about to issue its verdict, and our company's future is hanging in the balance. Her life hung the balance as medics rushed her to the hospital.

Be in a precarious condition or in a state of suspense. For example, The doctor said her life was hanging in the balance. This expression alludes to the suspended balance scale where an object is placed in one pan and weights are added one by one to the other pan until the two are balanced. [First half of 1400s]

A state of doubt or suspense regarding the outcome of something. The balance referred to is the old weighing device in which an object to be weighed is put in one pan and weights of known quantity are added one by one to the other pan, until the two are balanced. The unknown weight here is fate—that is, the outcome. The expression dates at least from the fifteenth century; it appeared in John Lydgate’s translation of the Fall of Princes (1430) and has been used ever since.