Final answer:
The winner-take-all feature of the Electoral College means that the candidate who wins the most popular votes in a state receives all of the state's electoral votes. This affects how presidential candidates from the two major parties run their campaigns and hinders third-party candidates. The Electoral College has not been abolished due to the difficulty of amending the Constitution and the belief that it helps maintain balance between small and large states.
Step-by-step explanation:
a) The winner-take-all feature of the Electoral College means that in most states, the candidate who wins the most popular votes in that state receives all of the state's electoral votes. This system applies in all but two states, Maine and Nebraska.
b) One way in which the winner-take-all feature affects how presidential candidates from the two major parties run their campaigns is that they focus their efforts on swing states. These are states where the outcome is uncertain and where they have a realistic chance of winning.
c) One way in which the winner-take-all feature hinders third-party candidates is that even if they receive a significant percentage of the popular vote nationally, they must win the popular vote in several states to have a chance of winning any electoral votes.
d) Two reasons why the Electoral College had not been abolished are the difficulty of amending the Constitution, which requires the approval of two-thirds of both houses of Congress and three-fourths of the states, and the belief that the Electoral College system helps to maintain a balance between small and large states.