In 2016, Hillary Clinton received nearly 3 million more votes than Donald Trump, but she lost the presidency because Trump won states with more electoral college votes.

PITTSBURGH (KDKA) – Both president Trump and former vice president Joe Biden have been crisscrossing Pennsylvania non-stop, and it’s not likely to let up. This state’s electoral votes are key to who wins the presidency – and both candidates know it.

Five times in American history, the loser of the popular vote has won the electoral college, and the White House with Donald Trump in 2016 is the most recent example. The electoral college gives an advantage to winning states, and makes states like Pennsylvania a real battleground this year.

In 2016, Hillary Clinton received nearly 3 million more votes than Donald Trump, but she lost the presidency because Trump won states with more electoral college votes – including Pennsylvania, which he won by seven-tenths of one percent.

“States like Pennsylvania are going to be incredibly important, and those are the states that people are looking at,” said University of Pittsburgh professor Kristin Kanthak.

Trump beat Clinton decisively in the electoral college by winning states like Florida, Michigan, Wisconsin, and, of course, Pennsylvania.

This year, Trump and Biden are campaigning hard in about a dozen states, ignoring the rest, knowing Pennsylvania could be the decider.

“I would be surprised if Pennsylvania doesn’t go with whoever wins,” said Kanthak.

With 20 electoral votes – determined by the number of representatives and senators in congress – Pennsylvania is a battleground and it’s possible this year the electoral college winner loses the popular vote.

“It really could happen again,” said Kanthak.