I think strategically they should encourage their voters to support whichever major party supports electoral reform (adopting a voting system that doesn't have the spoiler effect), and only vote third party if neither of them do.
In practice what this means is putting the Democrats on notice that they have to support RCV in every state, otherwise supporters of electoral reform will deliberately sabotage the party's chances and throw each election to the Republicans.
This is from the "don't mess with me! I'm crazy enough to do it!" school of thought, which worked so well against the "split or steal" choice given in a famous quiz show clip.[0] That game was deliberately designed to be equivalent to the Prisoner's Dilemma, just as the US voting system ends up being.
Electoral reform is a necessary pre-condition for a third party to have any power at the state or federal level at all.
It's not enough to have policies and politicians that appeal to people who currently vote for the major parties, you also have to convince them that voting for a third party won't lead to a worse party getting elected.
In practice what this means is putting the Democrats on notice that they have to support RCV in every state, otherwise supporters of electoral reform will deliberately sabotage the party's chances and throw each election to the Republicans.
This is from the "don't mess with me! I'm crazy enough to do it!" school of thought, which worked so well against the "split or steal" choice given in a famous quiz show clip.[0] That game was deliberately designed to be equivalent to the Prisoner's Dilemma, just as the US voting system ends up being.
[0] https://blogs.cornell.edu/info2040/2012/09/21/split-or-steal...