A responsibility of the vice president is to

become president if necessary

Explanation:

The vice president is a figure who can fit into different situations. For example, the vice president of a country is a person who replaces the president in situations where he is prevented, whether by travel, illness, death or impeachment.

There are, however, other types of vice presidents. In clubs or companies, vice presidents can be people who take care of specific matters. For example, in a club the vice president of football or in a company the vice president of finance (treasurer).

In the United States, the Vice President can be considered even "decorative" until he or she has to fulfill the intended duty if the day ever comes that something happens to the President of the Nation and the Vice becomes the President.

He/she is the first breaking vote in senate.