I am looking to explore the impact of 3rd parties on mainstream political parties in the United States. Not necessarily at the federal level but at state level too, and across any branch of the federal Government.

There are of course the most significant occurrences in history, such as Ross Perot's independent run in 1992 and 1996. But even more recently, the 2020 US senate election in Georgia saw the libertarian party deny either candidate 50% of the vote. Additionally, the green party was able to detract enough votes from Clinton in Michigan and Pennsylvania in 2016 to prevent her from winning. These are just some recent examples but of course there are many more. However, the above instances are mine, and others', mere assumption about which party the 3rd party impacted the most.

I'm looking to find if there has been any studies into the impact of 3rd parties in US elections, and which party their presence hinders the most. I've looked here, but the only available data was exit polling information, and I'm curious if there have been more rigorous approaches to examining this that go beyond exit polls.

This is my first question on this forum of StackExchange, I hope I have satisfied the requirements for a good question.

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    I don't see how this can answered. different third parties will affect the vote in non constant ways. A right wing third party might split the vote, but move the "centre of gravity" towards the right and so be harmful to the Repbulicans in the short term but beneficial in the long term. So it can be hard to decide exactly what you want to measure here.
    – James K
    Commented Dec 26, 2020 at 20:12
  • @JamesK, I'm sure pollsters have studied which parties have what sort of impact, and some things are reasonably constant over time (eg. the Libertarians and Republicans are drawing from the same general pool of voters, as are the Greens and the Democrats).
    – Mark
    Commented Dec 26, 2020 at 20:19
  • But my point is that a successful Green party can be good for democrats, in the long run. It attracts people who may come from Conservative backgrounds, but who have a single issue environment politics, expose them to left wing ideas, convert them to left wing supporters who then vote Democrat. It's not going to be a simple effect.
    – James K
    Commented Dec 26, 2020 at 20:22
  • I agree with @JamesK that there isn't likely to be a consistent answer. Third-party campaigns frequently rise and fall on the particular individual running in a given year and based upon other factors and their impact can vary a great deal. The general well established rule is that third-parties hurt major parties that they are closest too ideologically. But quantifying that is a case by case task..
    – ohwilleke
    Commented Dec 28, 2020 at 7:14


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