@Menachem
Daniel did not start the ge’ula process, Therefore, he could still be considered as a potential candidate. [if there will be a private thiyat hameitim].
Daniel never started. Therefore, he never failed. And therefore, he could still [at least according to one pshat in sanhedrin] be a candidate for mashiach.
But, As RAMBAN and RAMBAM point out, starting the ge’ula process and then,
dying & leaving unfinished business, equals failure.
Failure equals sheker.
Thats how we know now that j is a mashiach sheker.
Thats how we know that bar kohba is a mashiach sheker.
Thats how we know now that shabtai tzvi is a mashiach sheker.
Thats how we know now that the last leader of habad is a mashiach sheker.
They are all -equally- meshichei sheker.
Are the other possible disqualifications ? Yes.
For example the j personality and his actions, or shabtai tzvi’s conversion to islam, [or other possible problems with the personality of habads leader.]
The point RAMBAM and RAMBAN are discussing is : unfinished business.
Which is as clear as day disqualifying the late habad leader from being mashiach.
So clear is this , that [for the umpteenth time, again] habad itself [pre 94] considered this so axiomatic, that they were prepared to go so far, to the extent of building a new castles-in-the-sky theology , on this basis, proclaiming to all and sundry that their leader simply cannot die [!].
So, to our question : is the late leader of habad a mashiach sheker ?
The answer can only be:
a resounding ‘yes’.
All of klal yisrael, besides the majority of habad hasidim, know this answer.
They feel it in their bones.