The candidates are vying for electoral votes in a winner-take-all contest.

You may think that the voters choose the president, but that's only part of the story. The other part is the Electoral College. This is a group of people called electors who are chosen to represent each state. This map shows how many electors each state has. How many electors does your state have? The number of electors each state has equals the number of people that state has in Congress. Every state has two senators, but the number of representatives a state has is based on its population. States with higher populations have more representatives, and also more electors. Whichever candidate wins the most votes in a state wins all of that state's electoral votes. There are 538 total electoral votes, and whichever candidate wins a majority of those -- 270 -- wins the election.

Under this system, it's possible for a candidate to win the popular vote, but lose the election. That's exactly what happened in the 2000 election. George W. Bush got about 500,000 fewer votes than his opponent, Al Gore. But Mr. Bush won five more electoral votes, and won the election. The race was very close, and it all came down to who would win Florida's electoral votes. After several court cases and accusations of unfair vote counts, the Supreme Court ruled to accept a vote count that gave the state to Mr. Bush.