Ben West, I (to a much lesser extent) and a few other EAs worked on this in 2016: Vote Pairing is a Cost-Effective Political Intervention.

tl;dr: Ben estimates a personal counterfactual impact of 10 counterfactual votes in swing states for every hour of his labor (mostly software engineering), significantly higher than other plausible alternatives for work in politics.

Note that there was some pushback in the comments and also I think there's likely substantial diminishing marginal returns.

You might find this RCT interesting/helpful: https://alexandercoppock.com/papers/Coppock_trumptraders.pdf

Short answer: exploring this idea is a good idea ---vote swapping is a good idea and its basic common sense. But i'd just 'explore' it--the problem with vote swapping is most people who are sympathetic to it, or would be if they knew about --many have never of heard the idea--- and if they have won't actually do it. They find it too complex (as i did in 2016). Even registering to vote and then voting was too complex.

(Just as many people who are sympathetic to, or supporters of some candidate won't vote for that candidate---they just don't vote. I probably will not vote in nov 2020 elections--in my area it doesnt matter --this is an 'anybody but Trump' district).

unless you have a 'critical mass' its useless. so explore the idea, but don't put all your eggs in one basket or kill yourself promoting this idea. just keep it on the shelf (if you have a support network of people with similar ideas then you can explore it further--it might work). Lots of explorers perished, but a few hit the jackpot.

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longer answer:

This idea was developed a long time ago in my area by a local Green Party Member who is also a local politician (who is also nationally known--Jamin Raskin. I'm not sure if he is the originator of the idea.) . He said 'vote green' if you are in a safely democratic district; otherwise swap your vote with someone in a republican district and they can vote green party (GP) and you hold your nose and vote democratic.

i'm a member of GP though i actually do not like the the GP candidates--they seem to 'talk left, and walk right' and tend to be bullies, elitists, and opportunists.

I'm in a 90% democratic district. i did (hold my nose--i'm no fan of jill stein) vote GP in 2016 and also to legalize cannabis since i didnt like seeing people getting locked up for smoking a blunt on the street--it also costs money to deal with all these police, courts, and jails, besides wasting the time of people by locking them up---and then people later complain that they didnt go to school and get an education. (i was smoking weed almost starting in elementary school but i never went to jail for that (i have been locked up a few hours a few times for drinking a beer outside--which i did because its cheaper than going to a nosiy bar. ).

I almost regret voting for cannabis legalization because now its turning into another big business controlled by a few people.

I didn't do the 'vote swap'--too complex--but its a good idea. I think very few people did this---and this may be why Trump won---he won by a small margin, and a few of these green or other alternative parties may have made the difference (in places like Pennsylvania--which is about 50 miles from here ).

the vote swap was too complex--even voting is too complex.

(I actually sometimes think the people in the GP actually are Trump supporters . Many of them are already associated with RT media (russia today).

Alot of GP people are 'no compromise' --they will never vote for a democrat because they are not strict enough on the environemnt and other issues. They'd rather have Trump as a lesser evil rather than than having dirty voting hands. (Many of them are in fairly elite professional and academic positions so another 4 years of Trump won't affect them. If Trump decides to sell their favorite national park to an oil company, they'll just go their second favorite national park for vacation. )