Today, the country is caught up in an extremely tight presidential election, with the most recent national polls showing the Harris-Trump race within 2 points in either direction. That is an improvement for Democrats post-Biden, but the good news for Republicans is that the shift seems more a moment in time, not a trend.

There are many factors likely to influence the outcome of what looks to be another nail-biter election, including Tuesday’s debate. But in the last eight presidential elections, we have seen one key indicator of electoral success: the candidate who wins the popular vote outside California wins the presidency.

For both parties, historical trends show that the “rest of the country” margins align more closely with an Electoral College victory and can be a valuable measure of what will happen in November. Given the closeness of the race, there is a serious possibility that the Electoral College could determine the outcome rather than the popular vote.

This is a result of how close recent presidential elections have been. In the last three elections, the popular vote margin has been less than 5 percent. The last time the country saw three elections in a row with a winning margin of 5 percent or less was in the post-Civil War years of the late 19th century. From 1876 through 1896, the margins in all six elections were below 5 percent. This included two elections where the popular vote winner did not win the Electoral College, the 1876 and 1888 elections, a time when the country was so divided candidates could not build significant majorities and the Electoral College was in play.

Recent presidential popular vote data shows that more often than not, Democratic margins tend to be heavily concentrated in California. For Democrats, winning the rest of the country — 49 states — at a scale larger than California has been problematic in the last three elections. But the data also shows that Republicans have not won the popular vote at the presidential level since 2004. 

In looking at the elections from 2008 forward, in those four elections, a combined 64 percent of the Democrats’ popular vote margin came from California. If you add in New York, 96 percent of the popular vote margin came from just these two blue states. The other 48 states only produced a meager 4 percent of their margin. Hardly what would be characterized as a national majority coalition.

The reason this matters is that given the overwhelming Democratic advantage in those two states, Republicans (outside of a few congressional races) put very few resources into them, assigning campaign dollars where it can make a difference. 

As basically one-party states, California and New York give Democrats huge margins, skewing the popular vote nationally in the process. Given the serious fiscal and social problems of both states, the Electoral College gives the remaining states some protection from policies that don’t represent the views of most of the electorate.

The chart below compares California’s margins with the rest of the country from 1992 forward, with numbers in blue showing the Democratic margins, and red showing the Republican margins. Asterisks denote elections where the Electoral College winner did not win the popular vote.

2020: Joe Biden won the total popular vote by about 7 million but with 72 percent of his margin coming from California (about 5.1 million votes). 

2016: Donald Trump’s Electoral College victory came from winning the popular vote in the rest of the country outside California (1.4 million) compared to Hillary Clinton’s winning the national popular vote (about 2.9 million) that was heavily concentrated in California (over 4.2 million). 

2012: President Barack Obama won the popular vote by about 5 million votes, but about 60 percent of that margin came from California. However, he won outside California by close to 2 million votes.

2008: Obama won the national popular vote by over 9.5 million votes, winning by a significant margin outside California (almost 6.3 million) as well as by 3.2 million in California. 2008 is the last presidential election that a Democrat has won the rest of the country by a larger margin than in California. 

2004: John Kerry won California by about 1.2 million votes, with George W. Bush winning outside of California by over 4.2 million. That led to Bush winning the national popular vote by over 3 million votes. This election was the last time a Republican has won the popular vote in a presidential race — 20 years ago. 

2000: The 2000 election was another outcome where the eventual winner won in the Electoral College but not the popular vote. Again, we see a difference in the California vote (Al Gore won by almost 1.3 million in the state), but George W. Bush won outside of California by over 746,000. 

1992 and 1996: In both elections, Bill Clinton won more decisively outside of California than in California. In 1992, 26 percent of Clinton’s margin came from California, and in 1996, it was 16 percent. Quite a difference from the current situation, where for the last two winning Democratic presidential candidates, it was 60 percent or higher. 

After the close election results from a divided country at the end of the 19th century, both parties were able to build clear majorities, with 13 out of the next 15 presidential races having a popular vote margin of 5 percent or more. This spanned half a century, going from 1900 through 1956. 

The Electoral College process is more likely to result in national parties and their presidential candidates building governing majorities, rather than races so tight that we end up with presidents, unable to win more than a marginal coalition, faced with leading a country characterized by division and animus.

David Winston is the president of The Winston Group and a longtime adviser to congressional Republicans. He previously served as the director of planning for Speaker Newt Gingrich. He advises Fortune 100 companies, foundations, and nonprofit organizations on strategic planning and public policy issues, as well as an election analyst for CBS News.