It means that the activities that they do are just to bring the other person down (usually during campaigning)
The answer is 2.
PS I just learned that today
This statement is true.
When making foreign trading policies, things like tariffs decide how many things will be imported from where. If you have a most favored nation, you give them lower tariffs and thus motivate them to trade more with you and you help their economy. There can also be an opposite when you make tariffs higher for someone in order to reduce their importing.
