Ok, but in Canada a new upstart Conservative party (Reform) took away Votes from the existing Conservative Party (PC) and over several elections eventually got a majority.
So sure, Bernie might take away votes from the Democrats, but that doesn’t mean support will eventually shift to him.
Much more money and resources at play in the U.S., and Bernie is also fairly old and doesn't really have a 'party' or a clear successor. He/his followers wouldn't gain much from starting a new party.
So sure, Bernie might take away votes from the Democrats, but that doesn’t mean support will eventually shift to him.