Studies on presidential debates provide evidence that the use of boosters helps to convey strong emphasis on candidates’ ideology. This persuasive strategy is best portrayed through the schematic structure of presidential debates. Therefore, this study aims to scrutinize the boosters’ functions realized in the first American Presidential Debate 2020. This is a qualitative study with a pragmatic approach that investigates booster’s functions using the domain, taxonomy, and componential analysis. The linguistic evidence in the result shows the candidates exploited several intensifiers largely, including force indication, source tagging, accentuating, and solidarity markers. These boosters emphasize the strength of past deeds, criticizing past policies to promote definite proposals, expose repetitive emotional expression, and seek solidarity in the thesis stage. Meanwhile, in the argument stage, they function as devices for articulating offensive and defensive arguments. The results imply the essential functions of boosters in the persuasive political discourse of presidential debate viewed from its communicative purpose reflected in each schematic structure.