A Two-Round Runoff uses two elections. First, a "choose-one" election (often a primary) to narrow the field to two candidates, and then a second election (often a general, but in some instances a special runoff) between just those top two candidates. Runoff elections share some benefits with ranked choice voting such as seeking to uphold majority rule and the principle that you can support your compromise choice without hurting your first choice. But they have downsides.
Cost Savings and Campaign Finance
Cities or states can condense their two elections into a single contest on election day, saving taxpayer money. For example, citywide runoffs in New York City can cost at least $13 million, a cost that New York eliminated when they switched to ranked choice voting. Runoff elections in Texas and Louisiana also come with multi-million-dollar price tags.
Similarly, candidates in runoff elections must go back to their donors for quick cash to compete in the second election. Independent expenditures also rise in importance in a runoff election, able to be laser-focused with attacks on one of the two runoff candidates.
Prevent a Decline in Turnout
Because two-round runoff elections require voters to return to the polls a second time, they typically result in a smaller group of voters participating in the final round. Turnout in congressional primary runoff elections declines by an average of 38%, with runoff voters generally being less representative of the voting population as a whole.
With RCV, more voters take part in a decisive election. In RCV elections, each voter only votes once, ranking the candidates in order of preference. Some voters may choose to rank only some of the candidates. If each candidate ranked is eliminated during the count, such a ballot becomes inactive. However, even when taking into account the drop-off in voters between rounds in an RCV election, RCV still outperforms two-round runoff elections both in final round turnout and representativeness of the final round.
The chart below compares the turnout decline in two-round runoff elections to the number of voters in RCV elections who do not express a preference between the two finalists.
The election below is a real election from San Francisco in 2020. Seven candidates ran for Board of Supervisors in the 7th district to fill an open seat.
Below is a table of first-choice results.
Because these voters voted using ranked ballots, we can simulate hypothetical head-to-head matchups based on ranked ballot data. The chart below shows a table of all head-to-head matchups. The table is best read across rows. For example, the first row with data can be read as “Engardio is preferred over Nguyen by 52% of voters, Engardio is preferred over Melgar by 47% of voters, …”
We can clearly see that Melgar would win a head-to-head matchup against every other candidate, making her a consensus choice and the Condorcet winner.
A two-round runoff election would have advanced Engardio and Nguyen to the runoff election, where Engardio would have prevailed 52%-48%. Two-round runoff elections can fail to elect a consensus candidate if such a candidate is not in the lead in first choices. Such a candidate may be impacted by vote-spitting in choose-one elections, in which some voters from their primary base of support may have divided their support with another similar candidate.
Below are the ranked choice voting results.
Melgar consolidates support as trailing candidates are eliminated, until ultimately facing Engardio in the final round and defeating Engardio 53%-47%. Ranked choice voting elects a consensus winner, or a Condorcet winner, when a two-round runoff election would have failed to do so.