How different voting rules could kill the two

It's Election Day in the United States! Across the nation, millions of ballots are being cast. But what would happen if the rules of our electoral system were changed?

Dan Ullman asks that very question every time he teaches his course on math and politics at George Washington University, where he is a professor. He creates a mock electorate, complete with each voter's preferences, and asks his students to decide the winning candidate.

"There are three candidates and there are 99 voters in this little scenario that I made up, but it's made to be a very close election," Ullman says. "Any two different methods could lead to a conceivably different result. ... Different ways of eliminating or tallying the ballots can give different answers."

In fact, this year, some of those alternative methods are up for consideration on state and local ballots . And depending on whether they're adopted or banned, they could create very different outcomes for the regions they affect.

So today, we examine three voting systems representative of those alternative methods: Where they've been implemented, how they work and what they might mean for elections in the future.

Plurality voting

Often called "first past the post" voting, in plurality voting, everyone votes for one, and only one, candidate. The candidate who receives more votes than all the other candidates wins. For most American voters, it's the most familiar way to vote.

"It's very simple to run and it's very simple to understand for everyone. Everybody sees a very clear connection between how many votes were received and who gets elected, so for that reason at least, it's a very good system," says Romain Lechat , an associate professor who studies voting behavior and electoral systems at Sciences Po in Paris. "But it has disadvantages."

One problem is that plurality voting often doesn't result in an actual majority winner. Say you have three candidates: A, B and C. If, for example, 40% of voters pick candidate A, 45% of voters pick candidate B and 15% of voters pick candidate C; then, candidate B will be elected – despite the fact that more than half of voters did not choose this candidate.

Plurality voting is also vulnerable to vote splitting, when candidates with some similarity and potentially overlapping voter bases can pull votes away from each other. And THAT leads to the spoiler effect: when voting for a losing candidate ultimately affects which candidate wins .

The end result is that under plurality voting, voters are pressured to choose one of the two candidates or parties most likely to win... even if they don't actually prefer either. Especially in the U.S., where a 2023 Gallup poll found that 49% of Americans see themselves as politically independent, that could lead to voter discontent.

Ranked choice voting

Sometimes called instant runoff or single transferable vote, ranked choice voting is an increasingly popular alternative voting system . It's been implemented in state-wide elections in Maine and Alaska, plus in local elections for 45 cities across the country.

On a ranked-choice ballot, you vote for your top candidate – and you have the option to mark your second- and third-choice candidate.

"We constantly rank things in our head: What shows we're going to watch, where we want to travel, what we want to eat. It's not complex," says Caroline Tolbert , a professor of political science at the University of Iowa and an expert in ranked voting systems. "We rank our top three all the time."

Tolbert says ranked voting has a major advantage over plurality voting: It provides a majority winner. That's because the votes are tallied until a majority is found . If in the first count no single candidate has more than half of the votes, the candidate with the lowest amount of votes is removed and every ballot that originally went to this candidate is re-counted using second-choice preferences instead. At that point, if a single candidate has more than half the votes, that person is declared the winner. If not, the next candidate with the lowest amount of votes is removed from the count, and so on and so on.

Advocates of ranked voting say that it incentivizes candidates to campaign for second and third place on voters' ballots , which in turn creates a less polarized, more civil atmosphere.

It could also make candidates more active in terms of voter outreach, increasing voter turnout in the long-term.

But not everyone is a fan of the ranked voting system. It's a more complicated system by default. There's more room to express your preferences, but also more room to fill out your ballot incorrectly. Some experts say this makes it harder and more complicated to vote – and even causes more people to vote incorrectly and thus get their ballots tossed out .

Approval voting

Under approval voting, you're given a ballot with all the candidates listed ... and instead of just choosing one, you can fill in the bubble for as many, or as few, candidates as you want. Although this is one of the least common systems used in city, state and national elections, it's actually fairly common in daily life.

For example, if a big group of people are deciding between three types of food for lunch– tacos, ramen and pizza – they might ask people to raise their hands for each option that sounds good. People can vote for as many as they want ... and everyone goes to the restaurant with the biggest number of votes.

It's a fairly straightforward method: Voters can't pick too few or too many candidates the way they could in other systems.

"One of the big appeals for me as a scholar, but also, as you know, a second gen [immigrant], is its equity of access," says Whitney Hua , a doctor of political science and the director of applied data and research at the Center for Election Science , which focuses on approval voting. "We want to make sure that people who are from diverse backgrounds and from diverse education backgrounds can still understand how to vote."

Plus, it's simple to put into practice.

"We're talking like, it can be implemented the next day," Hua says. "This is just a simple change in the ballot language. ... This is great for election administrators right at the local level, all the way to state-level and federal-level elections."

Supporters say that's because it basically solves the problem of vote splitting – when candidates with overlapping voter bases pull votes from each other – basically making it spoiler-proof. And, like ranked choice voting, it discourages polarization .

"You can see that people take this opportunity to vote for several in order to both state what they want really, and also what is it is reasonable to hope," says Jean-Francois Laslier , a researcher who specializes in social choice, game theory and economics at the French National Center for Scientific Research .

One result of adopting approval voting, he adds, would be a multiplicity of candidates – a change for the U.S. "Very often you only have Republicans and Democrats. ... Almost everywhere else you have more candidates. If you were to change the system, you will end up with situations where you would have more. For instance, the parties could endorse several candidates," he says. "It would make things much easier for independent candidates. And that may change the system in a deeper way."

The downside? Approval voting is largely untested. It's been implemented in two U.S. cities – St. Louis, Mo. and Fargo, N.D. – in the past five years. Until we have more real-world examples, it's hard to fully understand the benefits and drawbacks.

So what's the best voting system of all?

When it comes to picking a voting system, mathematics is clear on one key point: You can't always make the majority happy.

In social choice theory, when it comes to evaluating voting systems, there's a famous result known as Arrow's impossibility theorem . It was proved in the 1950s by Kenneth Arrow, an American mathematician and political theorist.

"One of the things that underlies Arrow's theorem is the prospect that an electorate might like A more than B, B more than C and C more than A. That sounds impossible, or maybe irrational, but it absolutely can happen," says Ullman.

Although Arrow's theorem is primarily used for systems of ranked voting, where each voter has ordered preferences, even approval voting expert Whitney Hua says the main point still stands.

"No voting method can address all the criterion of what makes a good voting method," she adds. "You just need to choose which one of those [criteria] matters most to you."

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This episode was produced by Rachel Carlson, edited by showrunner Rebecca Ramirez and fact-checked by Tyler Jones. Kwesi Lee was the audio engineer. Special thanks to Cena Loffredo and Gilly Moon.