Strategic voting in Top 2 electoral systems
A Louisiana Primary system, used in Louisiana and in Georgia special elections is a modified Top 2 electoral system. In a Top 2 system multiple candidates run in one nonpartisan blanket primaries (candidates in all parties run in one primary). The top 2 candidates advance to the general election. In a Louisiana Primary system, the November General election is the primary, and if one candidate wins over 50% of the vote, they win election. If no candidates wins a simple majority, the top two candidates advance to a runoff. This is system being used for the Georgia Senate Special election between Raphael Warnock and Kelly Loeffler (the Georgia regular election (Ossof vs. Perdue) also has a runoff, but there was a partisan primary before it, meaning that in the November special election there was only 1 Democrat and 1 Republican on the ballot). The Top 2 system is used California and Washington.
In the article written before the November General election, some Democratic leaders and activists were calling for Matt Lieberman to drop out so as to not act as a spoiler for their preferred candidate Raphael Warnock. There were concerns that Lieberman could spoil the election for Raphael Warnock, either by picking off enough Democratic voters to prevent Warnock attaining second place and entering the runoff, or (more optimistically) preventing Warnock from earning a simple majority of the vote eliminating the need for a runoff.
If the two candidates that advance are from the same party advance, the other party would be locked out of the subsequent election and be unable to win. Theoretically if the North campus party had 60% support divided amongst 6 candidates that each get 10% support, and the West campus party 40% divided by two candidates that each get 20% support, under both systems I outlined above the North campus party would be locked out of runoff election, and therefore would not win the election, despite having 60% support from the electorate. This makes strategic voting crucially important in Top 2 electoral systems. If voters do not vote strategically, they could increase the chance that their least desired outcome (the opposite political party wins) comes true.
Both these systems allow to a political party to be looked out of the runoff or general election. The use of first past the post voting in most of the US, including in these relevant cases are examples of positional voting, where the most preferred candidate gets a ranking of 1 and all the other candidates get 0. The Louisiana Primary system and Top Two primary systems differ from simple plurality-winner elections are in the first stage of the election. In a plurality winner election, a voters most desired outcome is for their first preference candidate to win, and their least desired outcome is for their least-preferred candidate to win. However, under the Top Two system the prefer outcome is for your party’s candidates to lock out the other party from the runoff, and the least desired outcome is for your party to be locked out.
In the US the number of third party voters is relatively small, because third party candidates can act as spoilers. When voters vote for their preferred third party candidate they may increase the chance that their least favorite candidate will win the election. Another way to think about this logic is to vote only considering scenarios where you vote makes a difference. Since a third party candidate is unlikely to win, you shouldn’t vote for them, instead, you should vote for your favorite major party candidate because they might winner on a narrow margin, thereby making your vote relevant.
However, the Top Two system keeps the “third-party” effect in play in all elections, since there can be multiple candidates from the same party. In addition, a party may want two candidates on the chance that they may both advance.
This Top 2 system provides makes strategic voting import, but also makes strategic voting difficult. The information required to make an optimal strategic vote in a plurality winner election is simply to know which two candidates are most likely to win. In a Top Two primary, one needs to know by how much support every candidate has to each other. There can be an arbitrarily large amount of candidates.
In Georgia Senate Special election, the Democratic Party decided to not try an lock-out Republicans from the runoff election, likely because they thought they would not succeed and instead lock-themselves out. Instead, they tried to send a signal to voters to all vote for one candidate to ensure they make it to the runoff.
By Bryan Huang