How does ranked choice voting work?
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There are different ways to implement ranked choice voting, but all of them share the same core idea: voters rank candidates in order of preference.
The most common example is Instant Runoff voting, which uses the following rules:
* Tally up how many ballots each candidate appears at the top of.
* If one candidate has >50%, they win.
* Otherwise, eliminate the lowest candidate, and repeat.
Let’s take an example. Suppose that the 2020 US Presidential election had used instant runoff voting, and that there were four candidates: Bernie Sanders, Joe Biden, Generic Republican, and Donald Trump. We’ll take some example ballots:
* Voter 1: Bernie > Biden > Generic > Trump, that is, this person’s just really left-wing.
* Voter 2: Trump > Bernie > Generic > Biden, that is, this person’s anti-establishment and leans right.
* Voter 3: Bernie > Trump > Biden > Generic, that is, this person’s anti-establishment and leans left.
* Voter 4: Biden > Bernie > Generic > Trump, a pretty standard Democrat
* Voter 5: Trump > Generic > Biden > Bernie, just really right-wing
* Voter 6: Trump > Generic > Bernie > Biden, right-wing with some populist leanings
* Voter 7: Generic > Trump > Biden > Bernie, right-wing with some anti-populist leanings
* Voter 8: Biden > Generic > Bernie > Trump, generally pro-establishment and moderate
* Voter 9: Biden > Generic > Bernie > Trump, same as Voter 8.
In the first round, we tally up the first-choice votes for each candidate. In the first round, we have 2 votes for Bernie, 3 for Biden, 3 for Trump, and 1 for Generic. No one has 5 votes (>50% of the total), so we don’t have a winner yet even though Trump has the most votes. So we eliminate the worst performer, namely, Generic Republican.
That means we just delete Generic Republican from every ballot and repeat:
* Voter 1: Bernie > Biden > ~~Generic~~ > Trump, that is, this person’s just really left-wing.
* Voter 2: Trump > Bernie > ~~Generic~~ > Biden, that is, this person’s anti-establishment and leans right.
* Voter 3: Bernie > Trump > Biden > ~~Generic~~, that is, this person’s anti-establishment and leans left.
* Voter 4: Biden > Bernie > ~~Generic~~ > Trump, a pretty standard Democrat
* Voter 5: Trump > ~~Generic~~ > Biden > Bernie, just really right-wing
* Voter 6: Trump > ~~Generic~~ > Bernie > Biden, right-wing with some populist leanings
* Voter 7: **~~Generic~~ > Trump** > Biden > Bernie, right-wing with some anti-populist leanings
* Voter 8: Biden > ~~Generic~~ > Bernie > Trump, generally pro-establishment and moderate
* Voter 9: Biden > ~~Generic~~ > Bernie > Trump, same as Voter 8.
Only Voter 7’s vote changes, because they’re the one who ranked Generic first. Their vote shifts to Trump, their second choice. The count is now 2 Bernie, 3 Biden, 4 Trump. Still, no one has 5 votes, so we have to continue. The lowest-performing candidate is now Bernie, who is eliminated:
* Voter 1: **~~Bernie~~ > Biden >** ~~Generic~~ > Trump, that is, this person’s just really left-wing.
* Voter 2: Trump > ~~Bernie~~ > ~~Generic~~ > Biden, that is, this person’s anti-establishment and leans right.
* Voter 3: **~~Bernie~~ > Trump >** Biden > ~~Generic~~, that is, this person’s anti-establishment and leans left.
* Voter 4: Biden > ~~Bernie~~ > ~~Generic~~ > Trump, a pretty standard Democrat
* Voter 5: Trump > ~~Generic~~ > Biden > ~~Bernie~~, just really right-wing
* Voter 6: Trump > ~~Generic~~ > ~~Bernie~~ > Biden, right-wing with some populist leanings
* Voter 7: ~~Generic~~ > Trump > Biden > ~~Bernie~~, right-wing with some anti-populist leanings
* Voter 8: Biden > ~~Generic~~ > ~~Bernie~~ > Trump, generally pro-establishment and moderate
* Voter 9: Biden > ~~Generic~~ > ~~Bernie~~ > Trump, same as Voter 8.
This redistributes the votes or voters 1 and 3, who had Bernie ranked first on their ballots. The count is now 4 Biden, 5 Trump. Trump now has the required 50% of the vote (voters 2, 3, 5, 6, and 7) and wins.
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