Original sentence: Harvard is often considered a hotbed of political liberalism by the Right—Richard Nixon famously slandered it as the "Kremlin on the Charles"—while at the same time the Left often considers it the training ground for the Eastern Establishment
Edited sentence: Harvard is known for its liberal left-wing politics and has sometimes been called the "Kremlin on the Charles" (note that the city in which Harvard is located is sometimes called the "People's Republic of Cambridge")