In light of our discussion, we can explain that the root of the dispute between the tribe of Yehuda and the tribe of Binyamin was that, since the merit to be saved depends on rectifying the sale of Yosef, the one who is more innocent in this matter can effect the salvation. Binyamin claimed that his hands were completely clean, as he had not participated at all in the sale of Yosef, and with this merit, he would effect the salvation. On the other hand, Yehuda argued that although it was true that he initiated the sale (Bereishis 37:26), in the end, he rectified the matter by taking responsibility to return Binyamin, Yosef's brother from his mother, to their father with self-sacrifice (Bereishis 43:9). He was willing to fight for him against Yosef's warriors (Bereishis Rabbah Parsha 93, Siman 7), and eventually, he accepted upon himself to be a servant to Yosef forever in place of Binyamin (Bereishis 44:33). And indeed, in the place where baalei teshuva stand, even completely righteous individuals cannot stand (Berachos 34b). If so, his merit is greater than that of Binyamin, and with this merit, he would effect the salvation.