  We consider a problem of persistent magnetization precession in a single
domain ferromagnetic nano particle under the driving by the spin-transfer
torque. We find that the adjustment of the electronic distribution function in
the particle renders this state unstable. Instead, abrupt switching of the spin
orientation is predicted upon increase of the spin-transfer torque current. On
the technical level, we derive an effective action of the type of
Ambegaokar-Eckern-Sch\"on action for the coupled dynamics of magnetization
(gauge group $SU(2)$) and voltage (gauge group $U(1)$).
