Electoral College Worst-Case Scenario

A candidate could win 79% of the popular vote and still lose the election

This past U.S. presidential election was one of several in our history where a candidate has won the popular vote, but lost the Electoral College, and thus the presidency.

As of writing, Hillary Clinton’s popular vote margin stands at 48.2% to Donald Trump’s 46.5% (source). Over 2 million more people voted for Clinton than Trump, but Trump captured the 270 electoral votes needed to secure the presidency.

The percentage point difference isn’t huge, but is significant, and left me wondering: How bad can it get?

I set about to find the worst-case scenario — the biggest margin of popular vote that a losing candidate could get.

The data

First I made some assumptions:

There are only two candidates (I’ll call Purple and Green).

The number of people that voted per state in the 2016 election (as of Nov. 25, 2016) are the number of people that vote in this hypothetical election.

Every state is winner-take-all. In reality, Maine (4 electors) and Nebraska (5 electors), are not. See the Wikipedia article for more details.*

Second, I divided up the votes, trying to squeeze as much popular vote as possible for Green while still having Purple win the Electoral College. I did so by exploiting two features of the system: the voter-to-elector ratio discrepancies between states, and the winner-take-all nature of the electors.

Some states have a lower vote-to-elector ratio than others. This means that they’re over-represented in the Electoral College. A vote in one of these states “counts more” than a vote in a state with a higher ratio. For example, Wyoming has 3 electoral votes, but a voting population of only 300,000. In contrast, Oregon has 7 electoral votes and a much larger voting population of 2,000,000. By Wyoming’s ratio, Oregon would have 18 electors.

In order to maximize the losing candidate’s popular vote, I filled up the electoral votes of the winning candidate with these low vote-to-elector states like Wyoming.

I also took advantage of the winner-take-all nature of the College. If the winning candidate won a state, it would win by only 1 or 2 votes. But if the losing candidate won a state, it would get every vote in that state.

Result

The result is one candidate winning the popular vote 78.7% to 21.3%, but losing the Electoral College 267 to 271. On the map:

The road to 80%: in every state that Green wins, it wins every vote. In every state that Purple wins, it wins by one or two votes. This map has Green capturing 79% of the popular vote and losing the election.

The spreadsheet I used to play with these values is here.

Adjustments towards reality

While this situation is “possible”, we can be sure it’ll never happen. A candidate getting every vote in a dozen states, but drawing even in the others? No way.

We can make it more realistic by adjusting the numbers so that every state Green wins, it wins by a 20-point margin (60% to 40%) — a margin that occurs all the time in real life in some states. If we do this and keep the other states at virtual draws, we get Green winning the popular vote by 56% to Purple’s 44%, and losing the election.

For what it’s worth, giving these same states a 70/30 split — a rarer kind of margin to see, will put Green’s popular vote at 62%.

Alternatively, if we stop taking advantage of elector ratio discrepancies, we’ll also notice a drop for Green. To see this, we can reverse the advantage, so the winner fills up its electoral votes on high voter-to-elector ratio states like Oregon. If we do so, we’ll have Green with 71% of the popular vote and 265 electors, and Purple with 29% of the popular vote and 273 electors.

Conclusion

It turns out, a losing candidate’s popular vote lead can get pretty big. However, an extreme margin requires extreme voting patterns. Playing to the differences in elector-to-population ratios between states can have a significant effect, but playing to winner-take-all has the greatest potential to create a wide gap between the popular vote and the electoral outcome.

*Update: I quickly tried a configuration where I give both Maine and Nebraska to Green (Green sweeps every state that it wins). This gave 78.5% of the popular vote to Green, and 272 electors to Purple. So ~79% could happen even taking into account these electoral quirks.