What about the American states?
When it actually comes to the final presidential race, the Democrat and Republican candidates will go head to head to win the 50 American states - each of which has a certain number of electoral college votes, based on population.
This system matters, as the popular vote is less important than the electoral college vote. If Clinton's campaign is buoyed by big Democratic states such as New York, New Jersey, Illinois and California, these populous states could lead her to victory.
For example, in 2008, Barack Obama won 53 per cent of the vote - but this led to 68 per cent of the electoral college vote. Such highly populated states played a big part in this when they backed the current president.
Swing states - states that regularly switch between Democrat and Republican between elections - are also important.
States like Arizona, Florida, North Carolina, Ohio and West Virginia have the power to swing the election. So far, neither Trump nor Clinton has a significant lead in these crucial states.