I suspect you are quite wrong and will see a significant decrease in third party support vis a vis 2016.
I suspect you don't see the trend.
52.93% -> 51.06% -> 48.18%
45.65% -> 47.20% -> 46.09%
0.40% -> 0.99% -> 3.28% <== Having a female candidate will also up this count. (Jorgensen/Cohen)
0.12% -> 0.36% -> 1.07% <== With candidates and Ralph Nader supporting in the background (2.74% in 2000 for Greens) I expect this to go up. (Hawkins/Walker)
1988 -> 1992 event
"Trump’s job approval rating at this point in his presidency is lower than that of all of his recent predecessors except George H.W. Bush. The 38% of Americans who approve of Trump’s performance today compares with 29% for Bush in 1992. However, the two presidents’
disapproval rating is similar: 58% disapprove of Trump’s performance today, compared with 60% for Bush in 1992."
Low Biden enthusiasm and Low Trump enthusiasm is going to lead an uptake to these parties. If the democrats continue to suppress the left vote, they'll probably have to deal with a Libertarian funnel. Putting Ross to shame as they are already pumping out ads against Dems/Repubs.