From Chapter Fifteen of Rabbi Shloma Majeski’s Likkutei Mekoros, Volume 2. (Underlined text is the compiler’s emphasis.)
Translated by Boruch Merkur
According to the Gemara Sanhedrin 98a, one possible scenario that may play out with the advent of the redemption is that Moshiach will be, “righteous and victorious, a poor man riding on a donkey” (Zecharia 9:9). The Sages also said there that “[Moshiach will come] today, if you heed His voice.”
Thus (in the event that the Jewish people are only slightly meritorious), there is only one individual from among the righteous people of the generation who is fit to usher in the redemption. In fact, in every generation there must be a worthy candidate – if the Jewish people merit – to be the emissary for this mission, heralded by Eliyahu. But if they do not merit, he will be as other tzaddikim, without the distinction [of being Moshiach Vadai].
Upon the death of such a candidate, G-d forbid, there must be another worthy individual to take his place, as it says in Kiddushin 72b: “(One Master said: When Rebbi Akiva died, Rebbi was born; when Rebbi died, Rav Yehuda was born; when Rav Yehuda died, Rava was born; when Rava died, Rav Ashi was born – to teach that a tzaddik does not pass away from the world until a tzaddik like him is created, as it is said) ‘the sun rises and the sun sets, etc.’ (Koheles 1:5)” – see there.
In this manner, there was speculation in each generation as to the identity of the potential Moshiach. After the destruction of the Second Beis HaMikdash, it was assumed to be Menachem, as in the event described above [i.e., Menachem was born on the day of the destruction of the Beis HaMikdash]. And at the end of Menachem’s days, there was Rabbeinu HaKadosh. Thus, in the time of Rabbeinu HaKadosh they knew and declared that he is the one fit to fulfil this role. Following the passing of Rebbi, there was the one who spoke with Rebbi Yehoshua ben Levi, described in Meseches Sanhedrin. Afterwards, in the time of Rav Nachman, it was Rav Nachman. So it is in each generation – there must be one, should the Jewish people be found to be worthy, who is prepared to bring about the redemption. (Likewise, the disciplines of the Arizal recorded that in their time the candidate for Moshiach was the Arizal.) All of the foregoing is obvious and with this approach, all the words of Chazal are upheld.
If the Jewish people, however, are found to have “great merit,” there is another manner by which the redemption can unfold – it will be, “with the clouds of heaven, one like a man was coming (i.e., Melech HaMoshiach ––Rashi)” (Daniel 7:13), as stated there in Sanhedrin 98a. Thus, the Gemara says, “If he is among the deceased, it is someone like Daniel Ish Chamudos” – see there (Sanhedrin 98b).
(S’dei Chemed, pg. 1493)