The answer would be the first option.
Early vice presidents took an active part in frequently ruling
over proceedings of the body, with the president pro tempore only being called
on in the vice president's nonattendance. In the 20th century, the role of the
vice president changed into more of an executive branch position.
At present day, the vice president is typically perceived as a vital part of a
president's management and chairs over the Senate only on formal occasions or
when a tie-breaking vote may be desirable.
