Runner Advancement Rule

Question
There are runners on first and second.  The batter hits a ground the ball to the third baseman, since the third baseman is closer to 2nd he decides to run towards 2nd base.  He tags the runner as he is running back to second and touches second for a double play.  Does the runner have the option of running back to 2nd base to avoid the double play?   What would happen if the runner was tagged on 2nd as both men are at 2nd base?

Answer
First, yes the runner can retreat towards first base.

The runner that was being forced to advanced is not protected by being on the based as long as no preceding runners have been put out.  You could still tag out the runner that is on second that is being forced to advance.

Tom