Musar zu Schemuel I 8:5

Keeping all this in mind we can understand the meaning of Rashi's comment on 17,11: "Do not depart to the right or to the left," i.e. even if the judge tells you that (what you know to be) right is "left" or what (you know to be) left is "right." This interpretation was valid only when there was no king in Israel. Once a king was appointed, however, each level of administration had its functions clearly defined. In the opinion of Rabbi Eliezer Israel's sin consisted of their wanting to do away with this divison of responsibility between two different bodies. Israel committed a major error as soon as they asked for the king to act as שופט. Rabbi Eliezer divides the verse in Samuel I 8,5 שימה לנו מלך לשפטנו ככל הגוים into two distinct requests. One request was made by the elders, the second one by the people at large. The elders, who spoke about לנו, meant that the king would join them, as they were the judges already. This is why they did not say עלינו, "over us." The people at large, who entertained a different perception of the tasks to be performed by a king, said: שימה עלינו "place him above us" (Samuel I 8,5). They wanted the king to perform both the functions the Sanhedrin was designed for, i.e. משפט התורה, as well as those of a king, i.e. הוראת שעה.