To Win The Presidency, You Need to Win States
Imagine three US states of about the same size, where the same number of voters cast their ballots - with different political preferences:
1st state
In the first state, Joe Biden wins an overwhelming majority of the vote.


2nd state
In the second state there is a close race - slightly in favor of Donald Trump.


3rd state
Trump also narrowly wins in the third state.


But overall the Democrats have a clear majority of voters behind them - with 59.3 percent (16 of 27 votes).
Ultimately, however, the votes of the "electorate college" are decisive. And now it comes to a crucial step per state:
No matter how close the result is, the winning party sends all its electors of this state to the "Electoral College", the others go away empty-handed. And Trump, in our example, have suddenly a two-thirds majority.
This principle is therefore also called "Winner take all". It applies almost everywhere in the USA - except in Nebraska and Maine.
Not All Votes Have the Same Value
The "winner take all" principle intensifies the focus of the candidates’ campaigns on a few swing states, where a close race between Republicans and Democrats is expected. Because in the end only the votes in the Electoral College count: A total of 538 members elect the president on December 14th.
How many of those electors a state gets to send depends on the size of its population. States get up to 55 (California) - but at least 3. This minimum means that some sparsely populated states are overrepresented. If you compare the number of electors per million inhabitants the inequality is evident:
The electoral system dates back to the founding years of the United States at the end of the 18th century. Since that time, it has led to five candidates winning the presidential election despite having fewer ballots cast for them than their rival. Donald Trump is one of them: He, too, owes his victory in 2016 to this system.
How the 2016 election would have turned out without the "winner take all" principle

Trump

Clinton
The “winner take all" principle and the Electoral College of unequally allocated electors mean that individual voters’ votes differ in their “value”, depending on their location. But it’s not only those factors that distort the results of an election. Voting in the U.S. is above all a very active process.
Voters have to register to be able to cast their ballot - and often have to stand in line for several hours at one of the few polling sites. The registration process has been criticized repeatedly for making it especially hard for certain segments of the population to exercise their right to vote. This was also suggested by a report by the OSCE election observation organization ODIHR on the mid-term elections in the fall of 2018.
A New President Has to Be Inaugurated in January
In this election, there might be trouble with mail-in voting. Donald Trump has been railing against it, making baseless claims of the risk of voter fraud. Regardless of what battles might be fought over it, the schedule stands: On January 6th, the president-elect will be officially announced in Congress. He will then take his oath of office at his inauguration on January 20th in front of the Capitol in Washington, D.C..