How Likely Is an Electoral Vote/Popular Vote Split?

How Likely Is an Electoral Vote/Popular Vote Split?

By Sean Trende - October 12, 2012

The possibility that Mitt Romney could win the popular vote while Barack Obama wins the vote in the Electoral College has been discussed throughout this campaign. In recent days, we’ve seen pieces from Nate Silver, Nate Cohn, Harry Enten and RCP's Scott Conroy exploring the issue. Obama Campaign Manager Jim Messina has even referenced the potential discrepancy, urging reporters to look at the state polls rather than the national surveys.

How likely is this, really? History suggests “not very,” unless the race is extremely close. This is because the Electoral College and the popular vote almost always line up reasonably well.

Take a look at the following chart.

It lists presidential races going back to 1952 (prior to 1952, the ensuing exercise is difficult to apply because of the “Solid South”). The second column lists the state from which the candidate who won the popular vote received his 270th electoral vote. 

That’s a bit abstract, but think of it this way: In 2008, Barack Obama won Washington, D.C., by 86 percentage points, his largest margin of victory anywhere. That gave him his first three electoral votes. The next largest margin was in his home state of Hawaii, which he won by 45 points. That gave him four more electoral votes, for a total of seven.

Continuing this exercise (Obama won Vermont by 37 points for a total of 10; he won Rhode Island by 28 for a total of 14 . . .), we come to Colorado as the state that gave him the clinching electoral vote -- number 270.

The third column is the national margin for the candidate who won the popular vote. The fourth column is that candidate’s margin of victory in the state that provided him electoral vote number 270 (or would have, in the case of Al Gore).

The fifth column is the most important one. It is the “bias” of the Electoral College that year, which is the difference between the winning candidate’s popular vote margin and his margin in the state that gave him 270 electoral votes. Why does this matter? Because if tells us how far “off” the popular vote was from the Electoral College.

Take 1988. George H.W. Bush won nationally by 7.7 points. But he won the state that pushed him over the edge by 7.9 points. What this means is that if his vote share were decreased in every state by 7.700001 points, he would lose the popular vote, but still win the Electoral College by two-10ths of a point.

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Sean Trende is senior elections analyst for RealClearPolitics. He is a co-author of the 2014 Almanac of American Politics and author of The Lost Majority. He can be reached at Follow him on Twitter @SeanTrende.

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