Of course the deck is stacked against a third party. The Republican Party would have to dissolved the way that the Whig Party did after 1854 with the new party getting a substantial part of the old. Could not win in 1912 and might not win in 1916, unless the Democratic Party also fragments.
I agree that the two party system is the way to go, but the Republican party needs to get a spine.
Every setback the dems have had this year hasn’t been because of the republicans in DC. They have been bystanders, just watching from the sidelines.