not only is it possible, but it has happened and is currently happening in our lifetimes: either read a non-western history book to see several historical examples of political duopolies being overturned by 3rd parties (until the americans reversed it) or look for modern sources showing a 3rd party named morena overthrow its american backed duopoloy in mexico less than 10 years ago.
When did America decide to remove first past the post? Oh they didn’t …so how is 3rd party not a wasted vote?
not only is it possible, but it has happened and is currently happening in our lifetimes: either read a non-western history book to see several historical examples of political duopolies being overturned by 3rd parties (until the americans reversed it) or look for modern sources showing a 3rd party named morena overthrow its american backed duopoloy in mexico less than 10 years ago.