hang in the balance - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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]