Medicare is indeed a single payer system. Of course there are supplemental insurance programs out there, but they are all administered/controlled and approved by Medicare. Same elsewhere. I have single payer here in Europe, but pay a private insurance premium to ensure that I always have the choice to go to a private hospital anywhere in the world if I want, and that I will always have a single room, and so on. There will always be such plans available.But under the expanded Medicare For All plans that I have seen, the coverage will be more complete than with the current system (e.g., dental is covered, as are prescription drugs, and there is no need for so-called “Medigap”).
So regarding your reference to “financial math” — you are right that the Republicans are not alone in prescribing austerity for working people and the 99%; the Democrats have been doing that as well. But you should realise that the dire protests of “how are you going to pay for that?” are just so much kabuki theatre. The USA has a central bank and it has fiat currency. It can pay for ANYTHING. The Fed literally has access to an INFINITE amount of dollars. As long as we continue to be able to pay for things in USD, then we do not have to ever worry about running out of money.
I am sure you recall recently where 60% of Senate Democrats joined with the GOP to add an extra $80 Billion a year to the Defense budget. No debate. No one asking how we can afford it. And the only ones protesting in the Senate were Rand Paul and Bernie Sanders. They just added the $80 billion, which was $30 billion more than even Trump had asked for!
I suggest you read up on MMT — Modern Monetary Theory. Because that is the way the world really works. Financial capital is NOT finite — quite the contrary. When the GFC hit, the world’ s central banks created $21 Trillion in bailouts — OUT OF THIN AIR. There was nothing behind it; no gold reserves, no silver, no platinum. They created this money with a keystroke — just like they will create that extra $80 Bn going to the War Machine. The US banks got $4.5 Trillion from the Fed. They still owe $4.3 of it, and no one is worried or making a fuss. Because they can always make more if they need it.
As for “political capital” being finite, that is just a word salad. It is not political capital that makes anything happen, it is political WILL - and that will is as infinite as is the human spirit. Political capital is a worthless term invented by Beltway hucksters who want to seem smart. The only idiot who actually took the concept seriously was GW Bush. And you saw where that got him. No — it is political WILL that moves mountains, because it does not just exist in the politicians but in the electorate. Remember the old chestnut about FDR: he once met with a group of activists who sought his support for bold legislation. He listened to their arguments and then said, “You’ve convinced me. Now go out and make me do it.” LBJ said the same thing to MLK.
THAT is how things get done. And the amount of political will available in the country is infinite. But it doesn’t even take a lot. Ralph Nader is fond of quoting the idea that 1% of a population can force change if they mobilise.
You have been beaten down by neoliberal dogma. Time to free yourself and rise up.