"Alleged" Duopoly??
When's the last time we had a POTUS who was not a Democrat or Republican?
Save your Wiki click, it was Whig Zachary Taylor in 1848 ---- before the Duopoly existed. The Republican Party was years in the future and the Democrat Taylor defeated, van Buren, had himself organized that party just 15 years prior (and the Whigs were the same age).
The Republican Party was not a "third" party; it was another party in a time when multiple parties existed and two major ones --- Whigs and Know Nothings --- were taking their last gasps because neither one would address the elephant in the room of the era -- Slavery.
Duopoly means a closed system. It runs everything right down to the Presidential debates, and it's not about to allow any third party in on its racket. And the WTA/EC perpetuates that racket and ensures that we never get out of it.
As I said -- there's no argument to defend that.
The 1850s can occur again, so there is no hard Duopoly. Lots people like the current two parties, even more so today, but things change, and the electoral college won't stop things from changing. Teddy Roosevelt came close to unseating the two parties with his progressive run in 1912. He certainly sent Taft and the Republicans down into the gutter.
It's very much a "hard" Duopoly, I like the term. Again, the last non-Republican non-Democrat POTUS arrived 171 years ago at a time when both major parties were approximately fifteen years old. Today the major parties are 165, so they've had eleven times as much time to entrench Want to start a third party that gets enough attention to compete? Sure. All you have to do is deconstruct the monstrous two-headed system that runs the joint now, and rotsa ruck getting that Duopoly to let you into any debates, because they literally run it.
Which reminds of a quote by Al Gore's relative Gore Vidal:
"As far as a third party, we tried that in 1972, the People's Party. Unfortunately we hadn't remembered that in order to have a third party, you must first have two other parties". --- which just underscores that this entrenched Duopoly is not something I just discovered.
TR in 1912 siphoned off enough votes to come in second and push the Republican to third, which is the last time any 3P even achieved that much, but he was (a) a former POTUS well-known and (b) had come to the Republican convention with most of the primary delegates, so that was essentially the party deciding to go the corporate route and nix the progressive one, which cost them the election and enabled Wilson to take office with his 41% of the PV. But when Wilson left office, the next Republican challenger Harding won with the then-largest landslide ever, and barely had to campaign at all. So if the Duopoly was challenged by that, it sure shook it off with a quickness.
Just to put that in perspective.
I think if women had been allowed to vote, Teddy Roosevelt would have won in 1912. So again, the two dominate parties are not invincible. But, to the Republican and Democratic party's benefit, both have changed over time to survive and win. Most people can find something their looking for in either of the two party's.
In any event, the electoral college is not going away. There is not nearly enough support to amend the constitution on this issue. The other way of doing it with the NPVIC would get a lot closer to achieving the goal but is unlikely to ever get to 270. Even if it did get to 270, eventually several of the states would overturn the measure and return to awarding their electoral votes to the winner of the state popular vote.
Why would they do that? Especially after that state had already debated and passed the measure?
What would be the incentive? Under the NPV literally everybody's vote would account for something, even if they lived in Utah their vote would at least be counted in the PV, ergo they would have an influence they do not now have. Reverting to a WTA after teasing voters with actual relevance would be hugely unpopular. How do you make a case to your state saying "yeah you know how we gave your vote meaning a few years back? Cancel that out, your vote is going back to the scrap heap". Don't think that would sell real well.
Well, State A votes for the NPV. Then State A heavily supports a candidate that fails to win the national popular vote, but wins the state vote by a large margin. People get angry that their states electoral votes did not go to the candidate that a vast majority of people in the state supported. They protest and succeed in getting the state to go back to the old system of awarding the states EVs to the winner of the state popular vote. People will vote for and support the system that best supports the candidate they like. That's why NPVIC even if it gets to 270 will not last.
No I don't think that's at all realistic.
Once you've given the voters relevance ---- regardless who some candidate was in whatever year ---- they're not going to be keen to give it up.