The system allocates 538 votes across the country, and a candidate needs a majority, or 270 votes, to win. Here's how the Electoral College works. The college is the way American voters indirectly choose the next president and vice president through each state's electors.

In the race to 270 electoral votes, California and Texas are the biggest prizes, but all eyes are on seven battleground states that could decide the presidency. The state with the most electoral votes has 54 votes while the states with the least votes have three votes each.

Voters are heading to the polls in Michigan, a key battleground this year in the presidential election that also includes a high-profile Senate race.