The players: At least three people
The Bad Cop comes at the Subject hard, being aggressive and threatening, forcing the Subject into a defensive, combative, position.
The Good Cop then comes in with a moderate approach, soothing the Subject, positioning hermself as a friend or advocate of the Subject, if only the Subject can meet the Good Cop part way or otherwise co-operate.
The Subject is then manipulated into feeling that the Good Cop offers a reasonable choice, and if the Routine works, takes the Good Cop's offer--an offer that might not have looked so good were it not for the Bad Cop's preliminary treatment.
This routine is a stock element of some police dramas, but also in political thrillers in the context of a torture of dissidents, interrogation of prisoners of war, and like situations.
In a wider political context, radical parties or candidates can play the role of Bad Cop to the Good Cop of more centrist parties or candidates. Or a single party can play both roles at different times, for example by leaking news of a 2% increase in inflation (bad cop) a few weeks before announcing a mere 1% increase (good cop). The leak makes the announcement look better. (See also TrialBalloon and PushPolling).
The behaviour of the prosecutors of such a routine can be intentional. On the other hand, the effect on someone faced with extreme and less-extreme options can be similar to that of the Subject, without the effect having been intentional.