  There are a number of reasons to think that the electron cannot truly be
spinning. Given how small the electron is generally taken to be, it would have
to rotate superluminally to have the right angular momentum and magnetic
moment. Also, the electron's gyromagnetic ratio is twice the value one would
expect for an ordinary classical rotating charged body. These obstacles can be
overcome by examining the flow of mass and charge in the Dirac field
(interpreted as giving the classical state of the electron). Superluminal
velocities are avoided because the electron's mass and charge are spread over
sufficiently large distances that neither the velocity of mass flow nor the
velocity of charge flow need to exceed the speed of light. The electron's
gyromagnetic ratio is twice the expected value because its charge rotates twice
as fast as its mass.
