Vote trading this year (e.g., VotePair, which I registered with) and in 2000 (“Nader Traders”) attempts to mitigate the damage done to a major party candidate by minor candiates vaugely of the same stripe. However, there just aren’t many third party voters out there. From an email sent by VotePair yesterday:
We are very sorry that in the end, we were not able to pair every registrant, and hope that you nonetheless feel that your participation has been worthwhile. As we explained in an email to you last week, we received thousands more registrations from Democrats in safe states than from third-party supporters in swing states.
How about trading votes across offices and major parties. Specifically, Democrat voters agree to vote for a Republican congressperson when paired with Republican voters who agree to vote for the Democratic presidential candidate. This sort of trading would appeal to a less partisan and perhaps much larger segment of voters than single office major-minor schemes.
If (gargantuan if) large numbers participated the effect could be salutory. Keep that idea for the next time it makes sense.