did the working class ever hold political power in Bolshevist Russia?

[Erc]

Not too familiar with that period...

But you could argue that they really had most of the power for much of 1917.  The Soviets were probably more powerful (especially on a local basis) than Kerensky's government.  It probably didn't change all that much immediately after the October Revolution, but I really can't say anything about after January 1918.

[Erc]

Oh, you mean during the Civil War? Well, the working classes had the power that being on the right side of a gun gives you - the power to settle some very old scores. Most of the Red Army commanders were workingmen.

A lot of them were former Tsarist junior officers (and others in the Army who didn't get much respect--even Brusilov worked for the Reds), if I remember correctly.  Perhaps not from the best background in large part, but hardly proletarians.