A third party has become a main party 8 times in the history of the USA... regardless of any speculative principle (calling it a law is a bit of a joke), we have direct evidence the system isnt locked into two parties historically.
You are completely delusional if you think most voters, black or otherwise, have looked into Bidens past... The one thing I ask every person who supports biden is about his past... Of the hundreds of people I've asked who support Biden I can only recall one of them who ever knew anything about his past decisions or even knew the role he plaed in segregation at all.