Putting political considerations aside, what is Halachic basis for rejecting the primacy of Rabbanim in other political/religious camps? In the recent controversy over conversions in Israel, for example, we’ve had Haredi Rabbanim arguing that we should accept the Psak of Rav Eliashiv or Rav Vosner. We all understand the political considerations that may be involved in that argument, but what’s important to me is the Halachic basis for a modern Orthodox position. Simply dismissing Rav Eliashiv as lacking appreciation of Eretz Yisrael or the Klal (as I’ve heard from others) strikes me as a cop out. Certainly, there must be some logical, defensible position for selecting a Dati Leumi Derech.

The Chareidi approach on many different issues is diverse as well as the Dati Leumi approach to many different issues is diverse and I don't really know what exactly you are questioning. I can't speak for others how much more so for great rabbis; however there are numerous Halachic publications of many Zionist rabbis that explain in Talmudic-Halachic discourse, their approach and philosophy all of which have a strong and solid Halachic support.