Believing demagogue

Do they? Both, need to and do? Does a demagogue believe or need to believe in his or her demagogy? There are I think three possibilities. One is that the demagogue is rational. In the instrumental sense: demagoguing is the way to mobilise followers and advance one’s interests. The demagogical content is secondary. Is there a chance that demagogy will be successful to mobilise support? There is, if the demagogue’s followers or supporters are also