Nearly 2.9 million more Americans voted for Hillary Clinton over Donald Trump in the 2016 presidential election, but she still lost.

Trump won because he took the Electoral College, under a system set up in the US Constitution and refined through the centuries.

This is where the magic number comes into play. To win the White House, a candidate must win at least 270 electoral votes.

That's a majority of the 538 that are up for grabs in the 50 states.

THE NUMBERS

Each state is allotted a different number of electoral votes, based on how many representatives it has in the House, plus its two senators.

California has the most electoral votes with 55. Texas is next with 38 electoral votes. The candidate who wins New York or Florida can pocket 29 electoral votes toward the race to get 270. Illinois and Pennsylvania each have 20. Rounding out the top 10 list of states with the most electoral votes is Ohio with 18; Georgia and Michigan with 16 and North Carolina with 15.

TRUMP'S BEST PATH

Trump has several paths to 270, but his best route hinges on winning Florida and Pennsylvania. If he wins both states and holds onto North Carolina and Arizona, which he narrowly carried in 2016, and also Georgia and Ohio, which he won in 2016 but is now competitive, he will win. With 29 electoral votes, Florida is arguably the most crucial state for Trump. A loss there would make it nearly impossible for him to retain the White House.

WHAT BIDEN NEEDS

Democrat Joe Biden's campaign is laser-focused on the states in the Midwest and close by that Trump flipped in 2016 - Michigan, Wisconsin and Pennsylvania. He's also making a big play for Arizona, a state that hasn't backed a Democratic presidential candidate since 1996. Biden is also redoubling his focus on Florida, the biggest prize among the perennial battlegrounds and a state that would virtually block Trump's reelection if it swings Democratic.

Australian Associated Press