The first problem with the phrase “political science” is that “science” is a god-term in the U.S. Perhaps not as much as it was in the late 19th and early 20th Centuries, but many folks still hear “science” and think it’s a claim to a settled body of True Knowledge. (This is the regrettable way science is still often taught to students in elementary school and above; that, or as a cook-book approach to investigating the physical world, which is almost as sad.) Plus natural scientists and engineers held extremely high standing in the U.S. from the late 19th Century through most of the 20th century. So in choosing to name the discipline “political science” over a century ago, disciplinary scholars were no doubt aiming to crib some of the divine aura of “Science!” for themselves.
Further, during this time, “Science!” was tied up with the Whig narrative of ever-increasing Progress, human achievement, and human liberty; with the expectation of extending human control over the very forces of nature itself. “Social science” and “political science” aspired to share in this scientistic teleology, with disciplines purporting to develop scientific expertise regarding the human subject with the goal of improving (and controlling) human life and humanity itself.
We tend to forget how much pull terming something as “Science!” had during this period. Indeed, one of the real pulls of Marxism for American intellectuals in the first half of the 20th Century, as the Coen Brothers’ recent movie, Hail Caesar, hilariously reminds, was its claim to be a scientific theory.