To win the White House, a candidate must win at least 270 electoral votes, a majority of the 538 that are up for grabs in the 50 states, but not the popular vote.
Nearly 2.9 million more people voted for Hillary Clinton in the 2016 presidential election, but she still lost.
President Donald Trump won because he prevailed in the Electoral College, under a system set up in the US Constitution and refined through the centuries.
Currently, the path to 270 looks increasingly difficult for Trump, though Democratic challenger Joe Biden appears set to clinch it.
Biden’s path forward
Democrat Joe Biden’s campaign has a relatively easy and straightforward path forward. Biden maintained the so-called “Blue Wall” in the Midwest, flipping Wisconsin back from Trump’s 2016 win.
Biden is also doing well in Arizona, a state that has not backed a Democratic presidential candidate since 1996.
With Arizona included, Biden sits at 264 Electoral College votes. If Arizona holds, he can win any of the not-yet called battleground states, including Georgia, North Carolina, Pennsylvania or Nevada.
Trump’s path forward is much more difficult.
Trump currently sits at 214 electoral votes. Of Arizona, North Carolina, Nevada and Georgia, Trump needs to win at least three of those states.
If he wins three of those four, he also needs Pennsylvania.
Biden is currently leading the vote count in all of those, except North Carolina.
Each state is allotted a different number of electoral votes, based on how many representatives it has in the House, plus its two senators.
Trump is expected to be declared the winner in Alaska with three electoral votes, but that would not alter his path above.