WASHINGTON, D.C. — The chance is slim, but Hillary Clinton or Donald Trump could win the popular vote nationwide but lose the Electoral College vote and the presidency.

That’s because the election is not decided by the nationwide popular vote. It’s decided by electoral votes, with all of the votes for most states awarded to the winner of the popular vote in that state. (Maine and Nebraska award electoral votes proportionately.)

That happened 16 years ago in the disputed contest between Democrat Al Gore and Republican George W. Bush. Gore, the vice president at the time, won the popular vote, beat Bush nationwide by about 550,000 votes. But he was five electoral votes short of the 270 needed to be elected. Bush won the presidency.

“I think that’s probably less likely,” Republican pollster David Winston, said of a replay of 2000 this year. “I think you’re unlikely to see it unless it’s just really razor-close.”

The polls say Clinton leads nationally. But they remain close, some within the margin of error.

The gap between the electoral vote counts and the popular vote can be misleading. President Barack Obama beat Republican nominee Mitt Romney in 2012 by 4 percentage points, but that translated into a 126-electoral vote victory.

Michael McDonald of the U.S. Elections Project, a group that provides election data and research, said Clinton was better positioned than Trump to win the popular and electoral votes.

In the unlikely event of a split, he thinks Trump would carry the electoral vote and Clinton would lead the popular vote because of the expected high turnout of Hispanic voters in states like Texas and California.

For example, Clinton could get a much larger number of votes than Democrats usually get in a state such as Texas while still narrowly losing it and its Electoral College votes. That could help her carry the popular vote nationwide while not adding any electoral votes to her side.

Nate Silver at Fivethirtyeight.com suggested a week ago that if there were a popular-electoral split it would favor Trump, because at the time Clinton was not doing as well in swing states as Obama did four years ago.

Chris Lehane, a spokesman for Gore’s 2000 campaign, said political demographics that would contribute to the outcome Tuesday were different now than they were 16 years ago, making a split unlikely.

“Back in 2000, these demographics were not truly geographically reflected,” he said. “There was not a sizable Latino vote in a Virginia or North Carolina. The Latino vote was not so decisive in terms of the spread and the turnout was smaller. Millennials were not close to 30 percent of the overall vote.”

Lehane also said white college-educated voters were now a much larger portion of voters than in 2000, when they were more concentrated in the traditionally Democratic states. And the gender gap was not the factor then that it is in the 2016 contest.