RCV versus Two-Round Runoff

Ranked choice voting (RCV) and two-round runoff races are both multi-round systems that aim to promote majority support. Under these systems, a candidate reaches a majority once they have more than 50 percent of votes in the final round. However, under two-round runoff elections, voters are asked to return to the polls and vote a second time, whereas RCV accomplishes the same goal in a single election. Because two-round runoffs require two elections, they can result in a different group of voters participating in the final round than the first one: generally, fewer voters overall, and a less representative group of voters. 

Under RCV, the same group of voters can participate in every round. Some voters, however, may only rank some of the candidates. If each candidate ranked is eliminated during the count, such a ballot becomes inactive. Even when taking into account the drop-off in voters between rounds in an RCV election, however, RCV still outperforms two-round runoff elections both in final round turnout and representativeness of the final round.

The table below compares RCV or "instant runoff" races with delayed runoff races. It analyzes election results from 84 RCV races over the past two decades from 10 cities (San Francisco, Oakland, San Leandro, and Berkeley, California; Minneapolis and St. Paul, Minnesota; Santa Fe, New Mexico; Takoma Park, Maryland; Telluride, Colorado and Portland, Maine) and the State of Maine’s 2018 Democratic gubernatorial primary and congressional primary and midterm elections. These are compared with the 221 congressional primary runoffs stretching back to 1994, the 22 statewide runoff elections held in 2018, and the 14 runoff races which took place in San Francisco from 2000-2003, before the city started using RCV.

As intended, both runoffs and RCV resulted in every winner having a majority of active votes in the final round. However, with RCV, the winner’s median share of the vote in the final round was 48.8 percent of the first round vote, as compared to delayed runoff winners’ median of 37.2 percent in congressional primary runoffs, 34.3 percent in the San Francisco runoffs, and 36.4 percent  in statewide runoffs.


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The difference between RCV races and runoff races is even more evident when measured to 40 percent of the first round vote, the traditional measure of a “substantial plurality.” In the final round, more than 96 percent of RCV winners received 40 percent or more of the first round vote, while only 38 percent of the congressional primary runoff winners, 36 percent of San Francisco’s pre-RCV runoff winners, and 27 percent of statewide runoff winners achieved 40 percent of the first round vote. More than half of San Francisco’s 14 runoff winners earned fewer votes in the runoff than in the first round - a loss of support that cannot happen with RCV.

Not only does turnout tend to decrease by a much greater amount in runoffs than in RCV elections, but the proportion of people of color voting also decreases to a greater degree. The following chart shows that in federal primary runoffs, the proportion turnout of people of color decreased by 1.26%, while the proportion turnout for white voters increased by 1.18%. In statewide runoff elections, the proportion turnout of people of color decreased by 0.79% and for white voters increased by 0.78%. While average overall turnout decreases for all demographic groups in runoff elections, the decrease is greater for people of color, changing the demographic composition of voters from the first election to the runoff. 

People of color had drastically greater decreases in representation in runoff elections than did white voters, but the difference in decrease in RCV elections is much less. This may be because turning out to a second election poses a large time burden on voters--many people find it hard enough to make time for one election, much less two. This burden is felt differently by different socio-economic groups. Conversely, filling out an RCV ballot completely so that it is less likely to be exhausted takes a matter of seconds at the ballot box, and a few minutes of extra research at home. 


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Last updated 8/5/19.



We determined the demographics and voter turnout statistics for each district using voter data from L2. For estimated Citizen Voting Age Population (CVAP) L2 uses weighted census data. For voter turnout, L2 uses surname classifications. While this method is somewhat blunt, it does provide a workable estimate for voter turnout by ethnic group in prior elections. L2 groups voters into ethnicities and groups ethnicities into broad ethnic categories:

Additional methodology note for L2 VoterMapping: L2 has separate data by party for primaries, but not for runoffs. For example, data is available for everyone who participated in a Republican primary, but runoff data does not distinguish who participated in which party’s runoff. This is a problem because many of the runoff states have open primaries (meaning that just restricting voters by party in the runoff, as L2 allows you to do, doesn’t offer an accurate picture). To get around this issue, both primary and runoff data is filtered for the party in question. For example, if 1,000 Republicans participate in the Democratic primary, those Republicans will be excluded in the runoff (regardless of whether they turned out for the runoff or not) because of the filter for the Democratic party. In order to not skew the data, those 1,000 Republicans must also be excluded from the primary data. This is especially necessary when looking at changes in turnout by demographics because the different parties have different demographic compositions, so including different party's voters in the primary but not in the runoff would have a large impact on demographic data. Most elections don’t see many people voting in other parties’ primaries, so the exclusion should not have a large impact on data.

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