Americans casting their ballots today are not directly choosing the 44th US president. Technically, they are picking members of an Electoral College, so-called electors, who are pledged to one candidate or the other.
And it is the Electoral College and its 538 electors which will then formally vote to put a person in the White House. Some 270 votes are needed to win the election.
The number of Electoral College members allocated to a state is based on its representation in Congress. The smallest states have three electors. The largest, California, has 55.
Apart from Maine and Nebraska, it is a “winner takes all” system. Whoever wins the popular vote in a state is rewarded with all of its electors.
But, to become president, you do not have to win the popular vote nationally. Hence what happened eight years ago when George W. Bush won the US election, despite securing a smaller percentage of votes across the country than his rival, Al Gore.