There are several synonyms for the phrase "on the line" that can be used to convey similar meanings. One such phrase is "at stake," which suggests that something important or significant is in jeopardy. Alternatively, "in the balance" can be used to indicate that a situation is uncertain and could go either way. "On the verge" implies that something is about to happen, while "in jeopardy" suggests that something or someone is in danger or at risk. Finally, "on the brink" suggests that something is about to go over the edge or reach a critical point, and "in the crosshairs" implies that someone or something is being targeted or under close scrutiny.