The politician was known as a staunch ideologue who never compromised his political beliefs.

ideologue 是由名词 ideology（意识形态）加上后缀 -logue 构成的名词。ideology 指"思想体系、意识形态"，后缀 -logue 来自希腊语，表示"说话者、信奉者"。ideologue 合起来指"意识形态的坚定信奉者"，即"意识形态者"。