Final answer:
Displacement is the defense mechanism characterized by redirecting feelings from a previous relationship onto the current one.
Step-by-step explanation:
The defense mechanism that involves redirecting feelings from a previous relationship onto the current one is displacement. Displacement is when a person transfers their feelings, impulses, or reactions onto a different, usually less threatening target. In this case, the person is reacting to the current relationship based on what they need to see due to their unresolved feelings from a past relationship. For example, if someone had a negative experience in a previous relationship and felt hurt or betrayed, they might unconsciously project those feelings onto their current partner and react to them as if they were the cause, even if the current partner's actions do not warrant such a reaction.