How was the "manifest destiny" used by u. s. leaders as a way to explain their continental expansion?

They believed the land was rightfully theirs and that they had to conquer it, so they passed policies that could allow them to spread out among the nation and gather more land for the United States.

representative government

during the 20th century, the role of the vice president has evolved into more of an executive branch position. now, the vice president is usually seen as an integral part of a president's administration and presides over the senate only on ceremonial occasions or when a tie-breaking vote may be needed.