put a thumb on the scale

The phrase "put a thumb on the scale" means to unfairly influence or manipulate a situation in one's favor, usually by distorting the balance or fairness of a decision or outcome. It refers to the act of exerting biased or partial influence to tilt the results in one's preferred direction. This expression suggests an unfair advantage created by deceitful means, compromising the integrity of the process or judgment involved.