Hillary Clinton has built up such a disproportionate lead in California that it's possible -- should she end up losing a few key battleground states -- that she could get more votes than Donald Trump nationwide but still lose the presidential race.
It's not the most probable scenario. Nate Silver, an analyst at election tracking site FiveThirtyEight, puts the possibility of Trump winning the election but losing the popular vote at 12 percent. But it's become more likely as the race has tightened nationally while remaining lopsided in California.
To understand why requires a brief primer on the electoral college system and the current state of the presidential race.
In U.S. presidential elections, each state chooses electors to determine who wins. The electors represent the sum total of senators and representatives a state sends to Congress. Each state has two senators and a varying number of representatives based on population. Wyoming, a lightly populated state, has three electors because it has two senators and one representative. California, a heavily populated state, has 55 electors.
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With the exception of Nebraska and Maine, all electors in a state are supposed to go to the presidential candidate who wins the most votes in that state. So it doesn't really matter whether a candidate wins a state by three votes or three million. That candidate gets all the electors either way.
This can create a scenario in which a candidate gets more votes nationwide than the opponent -- but still loses the election -- because they didn't win the right mix of states. It happened to Al Gore in 2000, when he won the popular vote but lost the presidency.
For now, polls indicate Hillary Clinton will win enough key states to win the electoral college vote, according to FiveThirtyEight and the New York Times Upshot blog. But polls also show her edge in the popular vote shrinking. As her lead falls nationwide, it increases the chances she has lost ground in critical "swing" states, which in turn increases the chances that Trump could pick up enough electoral votes to win.
But even in this scenario, Clinton's lead in California is so huge it could keep her ahead in the popular vote. Recent polls show her winning the state by 20 to 25 percentage points.
If turnout is similar to 2012, that would translate to Clinton receiving 2.5 million to 3.5 million more votes than Trump in California -- equivalent to roughly 2 percent of the votes cast in a typical presidential election.
This chart shows the vote advantage or disadvantage Clinton has by state, based on FiveThirtyEight's polling averages and 2012 election turnout. The first bar shows an election with turnout at 85 percent of what we saw in2012; the second bar shows an election with turnout at 115 percent of 2012 levels.
Sources: Vote margin estimates from FiveThirtyEight; voter turnout data from uselectionatlas.org