The Alter Rebbe of the Lubavitch, R. Shneur Zalman of Liadi, is reported to have said, surprisingly, that Moshiach will be a Misnaged (not a Chassid), giving the following explanation.
If Moshiach will be a Chassid, the Litvaks (Misnagdim) won't accept him. But if he will be a Misnaged, the Chassidim will accept him anyway, since Chassidim are (allegedly) 'kabbolas ol'niks' (בני קבלת עול).
If so, how did the messianic fervor around the late Lubavitcher Rebbe take off? Did they abandon the above teaching of the Alter Rebbe, renowned and venerated founder of the Habad Lubavitch group?
By the way, if you think about it, the above saying is really a Chassidic put down of Misnagdim. As if they (the Chassidim) are saying that the Misnagdim are like babies, they won't accept a Moshiach not like them. But we are more mature, we won't insist that Moshiach will be one of us. Reminds me of the issue of Moshiach's Hat.
P.S. Does anyone know of sources for the above, especially early ones? I did a search online and saw it mentioned in a number of places, including a Lubavitcher forum. Even a very prominent Lubavicher Chassid, R. Zalman Posner, longtime Lubavitcher shliach in Tennessee, mentioned it in the course of a back and forth on Lubavitch messianism in Jewish Action magazine a few years ago (page three, first column, paragraph three). So it is known. Though how well known these days, I do not know. Perhaps Lubavitchers didn't talk about it much in recent times. Perhaps it fell out of favor. It wouldn't seem to fit in too well with those promoting the late Rebbe as Moshiach I bet. :)
Addendum - see here for a source from the last Lubavitcher Rebbe.