  We study a possible correspondence between the softening of the wobbling mode
and the "phase transition" of the one-dimensionally rotating mean field to a
three-dimensionally rotating one by comparing the properties of the wobbling
mode obtained by the one-dimensional cranking model + random phase
approximation with the total routhian surface obtained by the three-dimensional
tilted-axis cranking model. The potential surface for the observed wobbling
mode excited on the triaxial superdeformed states in $^{163}$Lu is also
analyzed.
