As reflected by the length of the article in which it is described in the Constitution, the Founders expected the branch to be the most important.

The electoral college consists of 538 electors. a majority of 270 electoral votes is required to elect  the president. your state's entitled allotment of electors equals the number of members in its congressional delegation: one for each member in the house of representatives plus two for yoursenators.congress does the electoral college represent

The one that most represents the earths mantle would be the skin since the mantle is the upper part of the earths depths which is just like the skin of an apple.