In what way did the Nesi'us of Elazar (in his capacity as 'Nesi Nesi'ei ha'Levi') manifest itself?
Rashi: All the appointments among the Levi'im were made by him. 1
Targum Yonasan: He was responsible for consulting the Urim ve'Tumin regarding any She'eilah that arose among the Levi'im that required Divine guidance.
Rashi: As implied by the continuation of the Pasuk. Refer also, to 4:27:1:2. (It is not clear however, seeing as Elazar was overall in charge of Kehas, and Isamar, of Gershon and Merari - See 4:28, 33 - what role Elyasaf ben La'el, Elitzafan ben Uziel and Tzuriel ben Avichayil, in their capacity as the Nasi of Gershon, Kehas and Merari respectively, played)? Refer to 4:27:1:2 2