Thoughts on US Third Parties.

This comes from watching the French election, which is a similar legislative-executive system to the US.  I will also admit to voting Green from a disgust with the US duopoly (i.e., the Democrats and Republicans) and its stranglehold on the system.
In a way Dan Savage is correct, the third parties should be running candidates lower down the ticket, in particular for the legislature. That is because a third party would be more effective in pushing its agenda there, or at least in blocking other parties from pushing theirs. It is more effective to be a spoiler/fixer in the legislature than in an election.  Third parties will become a force to be reckoned with once they demonstrate they have power, but they need to be the force to do what the obstructionists in congress have been doing. Or to thwart the obstruction.
One of the Clintonista/Democrat talking points was that the party is a coalition of various political views, but the duopoly parties are failed coalitions.  In some ways, they have become titular left-right parties, although I would argue any difference is more in appearance and relation to hot button issues (e.g. abortion and gun control [1]).  The past election showed how detrimental relying upon hot button issues is to real issues (e.g., the environment).
Third parties are good for keeping politics real. Case in point are the presidential debates which are no longer run by the League of Women Voters.  The president of the LWV, Nancy M. Neuman, denounced this action when the LWV ceased having any real control over the debates:

"It has become clear to us that the candidates' organizations aim to add debates to their list of campaign-trail charades devoid of substance, spontaneity and honest answers to tough questions," Neuman said. "The League has no intention of becoming an accessory to the hoodwinking of the American public."
Neuman said that the campaigns presented the League with their debate agreement on
September 28, two weeks before the scheduled debate. The campaigns' agreement was negotiated "behind closed doors" and vas presented to the League as "a done deal," she said, its 16 pages of conditions not subject to negotiation.
Most objectionable to the League, Neuman said, were conditions in the agreement that gave the campaigns unprecedented control over the proceedings. Neuman called "outrageous" the campaigns' demands that they control the selection of questioners, the composition of the audience, hall access for the press and other issues.
"The campaigns' agreement is a closed-door masterpiece," Neuman said. "Never in the history of the League of Women Voters have two candidates' organizations come to us with such stringent, unyielding and self-serving demands."
Neuman said she and the League regretted that the American people have had no real opportunities to judge the presidential nominees outside of campaign-controlled environments.

lwv.org/press-releases/league-refuses-help-perpetrate-fraud
I would that change is drastically needed in US politics, particularly its system of elections, but that will not come as long as the duopoly holds power.
I have pointed out that the Electoral College needs to be abolished, yet the fact that Clinton's "loss" was due to her failing to secure enough votes in the Electoral College is again overlooked and substituted for blame on everything except the existence of that body (as was the case in 1990).  Both times the "losers" won the popular vote.
Of course, abolition of the Electoral College is only one thing in what is probably a long wish list of electoral reforms needed in the US:

open debates run by an impartial body like the League of Women Voters, shorter election cycles, open primaries, ranked choice voting, return of the fairness doctrine and equal time rule (Trump used the lack of it to get shitloads of free publicity), campaign finance reform--if not publicly funded campaigns, easier access to the ballot for parties, reform or abolish the electoral college, end gerrymandering, handcounted paper ballots or receipts, and I am sure that is only the beginning.

While one can dream that there will be internal change, it doesn't seem likely since the parties still seem entrenched in the same behaviours which have led to the US political system being the disaster it is.
OK, we also need to add in media consolidation here since it is one way the "state" can get away with  form of censorship, but only allowing one message to get out.  Also controlling any opposing voices.
Any real change has to come through the system since violence will backfire and result in the wrong type of change.  Thus any dissenting parties best chance has to be to try and thwart the duopoly and use the duopoly's power against it.
Change has to come, but it must come by using the system to gain power and then force change.
[1] This is not to say gun control is not important (or abortion), but these issues have been used to get people to vote against their interests.  Neither is one of left and right, but of public welfare and safety.