Would it be permissible to believe that Jesus is the messiah if that belief otherwise entails no rejection of halakha or Jewish tradition?
"Messianic Judaism" is generally speaking Christianity repackaged in a Jewish veneer, so they have the same beliefs on the Torah and the divinity of Jesus/Trinity as mainstream Christianity. But ...
During the times of false messiah Shabbetai Tzvi, and for several decades afterwards, many well established rabbanim  believed him to be Moshiach. Some even maintained this belief after his ...