The United States does NOT have a "national election". This must be distinctly understood, or nothing wonderful can come of what I& #39;m about to tell you. Instead, every four years, the US has 50 STATE elections - plus DC & US territorial elections - all at the same time.
Each state (plus D.C.) is granted "electoral votes" which are equal to the number of representatives they have (based upon population), plus two senators. There are 538 total Electoral Votes. To win, one must capture 270 EVs (more than half of 538).
This complicated and undemocratic method of election was devised by our Founders for two important reasons: to prevent any single person from winning based upon popularity, and to restrict the larger states (specifically urban centers) from dominating elections.