No, RCV does not help third parties, and I have the receipts:
1. Australia’s 100-Year Experiment with RCV
The most conclusive proof of RCV’s impotence in the face of a two-party system is clear to see in the one country which has used it for the longest. For a little over a century, Australia’s House of Representatives has used single-winner RCV, and their Senate has used a proportional system.
I should stress is it is well established that proportional systems do help third parties; and the Australian Senate (being proportionally elected) has enjoyed a decent amount of third party participation throughout its existence.
Contrast this with the Australian House. As shown below, there is almost a 50-year span during which the Austrailian House used RCV and had ZERO third party membership. Surely if RCV helped third parties, this would not have happened - especially while third parties were doing absolutely fine in the Senate.
Furthermore, let’s compare this with the performance of third parties in US Congress:
It is a very similar picture. In both US Congress and the Australian House of Representatives, third parties have had stints of shallow activity, and long spells of absence.
The rational conclusion here is RCV has a track record of not helping third parties whatsoever. Additionally, it demonstrates any theories that RCV just needs several elections to work don’t hold water.
2. Other Correlations Between RCV and FPTP
Additional observations suggest RCV is just an iteration of FPTP. A 2.0 version of the current system, that comes with extra baggage. That’s not to say there aren’t differences - but the differences are too small to matter.
For instance, let’s look at how RCV results are reported, compared with other election methods. Here are the results of an exit poll from the 2012 election, in New York City:
Obviously this particular district is biased heavily left, in favor of Obama. However, what we’re interested in is how third parties performed, compared to FPTP results.
On the top panel, FPTP results (blue) are compared with Approval results (orange) and Score results (green). Note that Stein, Johnson, and other third parties all perform quite well - in fact, they all surpass Romeny’s measured support. This is to be expected, given the left-bias of the district. These are clearly the kinds of results we should want to see from our elections.
Moving on to the lower panel, we see FPTP compared with RCV (red). There is no apparent difference in the reported results. Third party support remains hidden, and Romney is still measured to be a “better” choice for the district than any of the third party candidates, in spite of our knowledge this is most assuredly not true.
Another indication of RCV’s similarities with FPTP comes from FairVote, the largest pro-RCV advocacy organization in the US.
Here, FairVote describes data they have regarding “come-from-behind winners” in all RCV elections that have happened so far in the US:
Summary: In 93% of RCV elections, the candidate with the most first-choice votes won.
This again suggests an incredible amount of agreement between RCV results and FPTP results. Even if you say “well, that’s still a difference of 7%”, that’s not exactly true; 7% is the maximum possible difference. This is because in real FPTP elections, voters are strategic. They anticipate the results, and shift their support the same way RCV would. It is not unrealistic to think the actual figure is 5% or lower.
Again, I must stress how voter behavior in FPTP already follows the RCV algorithm. Voters withdraw support from their true favorites, and move it to more “viable” candidates. This is literally all RCV is automating behind the scenes, with the ranks: “non-viable” candidates are eliminated from consideration, and support ultimately goes where a viability-aware voter would have put it in FPTP.
If you oppose FPTP on the basis that it hurts third parties, this degree of agreement between FPTP and RCV should be a serious red flag.
3. The Spoiler Threat as a Negotiation Tactic
This last point relates to a point of power FPTP actually gives to third parties, which RCV takes away. Even if you view the above data with skepticism, or reason that there are still minor benefits RCV affords third parties, I encourage you to also consider there are definite negatives.
In this case, I’m talking about the consequences major parties suffer in FPTP when they don’t broaden their base to include adjacent third-party voters.
In our current system, third parties actually have some leverage on policy and which issues receive the most air time. When a major party ignores them, or refuses to make concessions, they lose votes to them. So major parties try to appease them.
Indeed, consider the current presidential election: Donald Trump attended the Libertarian party convention in an attempt to broaden his coalition; and the Green party is trying to extract concessions related to Gaza from the Democrats.
RCV advocates claim their system also encourages this. But unfortunately it doesn’t. Consider: The effort required to persuade voters to rank you 2nd is inherently less than the effort require to persuade them to withdraw support from their 1st choice and give it to you. So it follows that FPTP demands more serious concessions to would-be third party voters than RCV.
Conclusion
It makes no sense for third parties to support RCV. It has a history of perpetuating two-party systems, gives no indication of meaningful change, and in fact compromises the one bargaining chip third parties do have.
What you accuse STAR of, I accuse RCV of: It is a divide-and-conquer distraction. An illegitimate reform, sold on puffed-up, and often outright false claims.
If you want to help third parties, do not, under any circumstances, support RCV. Instead, you should support STAR, Approval, or proportional systems.