The vocal disbelievers were sufficiently powerful that they could not only set a deadline, but also presume to be able to enforce it. This confirms that they were in political power. They set a day when they would officially declare the prophecy unfulfilled. They would also use that occasion to purge the Nephites of those believers who contradicted them.
With that terrible prospect, Nephi, the son of Nephi (the Nephi who had been promised that he could seal on earth as well as in the heavens (see Helaman 10:7)), that son of Nephi, who had not received the promise that his father received, but who believed along with his father, knelt to pray to God on “behalf of his people, yea, those who were about to be destroyed because of their faith in the tradition of their fathers.”