The significance of the Electoral College in U.S. presidential elections lies in its role as the mechanism through which the President and Vice President are elected. Established by the Constitution, it consists of 538 electors, with a majority of 270 votes needed to win. This system can lead to scenarios where a candidate wins the presidency without winning the popular vote, as voters in each state choose electors pledged to specific candidates. It reflects the federal nature of the U.S. government, balancing power between populous and less populous states.