why, according to garraty, has the growth of presidential primaries made the selection of the vise president less democratic

According to John Garraty, the growth of presidential primaries had made the selection of the vice president less democratic because only the elections for the presidential candidate nomination are conducted within the party.

Explanation:

The parties that contest elections are mostly inclined towards and interested in the election of the presidential candidate and it is observed that not many care who the party's vice-presidential candidate is. The vice-presidential candidate is usually directly chosen and not elected by the party members like the presidential candidate is elected.